You are probably aware that internet connectivity in China is limited.  Don't expect to be able to access Facebook or Google, including gmail and Google Maps, unless you have installed a VPN on your device.  Even then, just because your lodging says you have internet access, you may find that it's either very slow, or very sporadic, or both.  You may be able to access your email, depending on where you are and what email service you use, but a VPN might be helpful insurance.  The Chinese government recently has begun a crackdown on VPN services, as many Chinese have been using it to get around the ban on some social networks and some news sources.  Do not depend on having it available.  You may wish to warn your friends, family and associates that your connectivity likely won't be as immediate as they are used to.  

If you want internet data only, then you can buy a USB 4G wifi hotspot device with China SIM included for a set time period (e.g. 30 days) and data limit.  They also can be used to connect your wifi tablet or computer through VPNs.

If you plan to use your cell phone in China, be sure to check with your carrier BEFORE  you go and do anything you need to so that you can use roaming in China.  You may find that roaming charges are so high you'll only use it in emergencies, but at least that way it will be an option.  Check if a data plan is available at a price you're willing to pay; the price very well may be prohibitive.  If you are used to using your smart phone for navigation using on-line maps, you may find yourself deprived of a valuable resource if you don't plan ahead.  This is compounded if you don't speak or read Chinese, as very few Chinese people will be able to speak enough of your language to help you, save at hotels that cater to foreigners and at areas visited by many foreigners. The best solution, and probably the most cost-effective is to purchase a Chinese SIM with a data package.  

A little planning ahead can save you a lot of frustration.  It's not easy to learn enough Chinese in a short time to be really useful, and a combination of your difficulty in speaking and the wide variation in dialects in different areas of China won't make it any easier.  If you're taking a smart phone or a tablet computer, though, you should be able to find free or inexpensive apps that will help you get where you want to go and allow you to get at least an idea of the various items on a menu or otherwise order food, or even buy some widget when you don't even know the Chinese name, let alone how to actually ask for it and negotiate a price.

First, a mapping program.  You should be able to find a map program that uses off-line maps that you download.  The map file(s) for China will be large, so you'll want to do this where you have good internet access.  If your device has a GPS (built-in or as an accessory), the map program should be able to show you where you are.  One such program is OsmAnd; the current China map release has detailed street-level information for most large cities and areas where tourists would normally visit.  There are likely other programs with similar capabilities.  The important things to check are the ability to use the program and maps when not connected to the internet, and the suitability of the maps available for the places you plan to visit.

Second, a dictionary program (try Google translate app). You may not be able to type in Chinese characters, or at least not quickly enough to be much use, but you should be able to type in English words and have the Chinese displayed, so you can show that to a merchant or server.  It's helpful if the dictionary program has a "history" function, so you can type in a small number of words that go together to describe what you want, and show all that at once to someone.  You'll probably find that many (but not all) Chinese are quite happy to try to communicate with you, if you will meet them with your best effort.  Repeating an English word to them in a louder tone just is NOT going to help!  But showing them something they do understand will engage with them.  Some dictionary programs also have character recognition:  they can actually read Chinese characters.  The problem is that the characters commonly have multiple meanings, so you have to be able to use the context and whatever other information you have available to make sense of things.  For example, one of the most helpful uses of the character recognition is in deciphering menus.  If you see one translation that's food-related and others that are not, for some particular character, most likely it's the food one that applies in this case.  Your understanding may not be perfect, and expect that sometimes you will get things that are not at all what you thought they would be, but...be adventurous.  You may well discover something you really like that you'd never have thought to try otherwise.  Once you've identified a menu line you want to order, simply pointing to it to show your server, and raising one finger to indicate you want one order of that item, should do the trick.  To get you started in your dictionary search, you might try Pleco and Hanping.  Both are available free, for Android at least, though the character recognition is for a small fee.

Third, a hint.  If the dictionary just isn't helping, remember that "a picture is worth a thousand words."  If you can take a picture of what you are looking for, or capture one from the internet, and show that to a merchant. that will often get the negotiation started. You may find a merchant that just doesn't want to deal with you; recognize that fact and don't waste your time and his.  You may find one who would like to help you, but doesn't have what you want and often will try to sell you what she has.  Don't be afraid to say no, shake your head, and walk away.  But it can be a joy working with a merchant who honestly tries to take care of exactly your needs, using pictures, dictionary, hand signals, whatever works.  Another place where a picture works well is for a restaurant that has pictures of entres outside before you enter; you can take a picture of their pictures and show it to the server and point to what you want.  It's common to bargain for merchandise in smaller shops.  Arm yourself with an idea of what something is actually worth...what you'd pay for it at home, at the very least...and counter-offer with something lower than that.  You won't normally get the merchant to accept your offer (unless you've made it too high!), but you may agree on something in the middle.  Again, don't be afraid to say no and walk away.  And don't be surprised if that elicits a lower offer from the merchant!  Understand that, even if you've haggled for five minutes with the vendor, you are under no obligation to buy if you're not happy with the price and the merchandise.

A lot of this information is appropriate for use mainly in areas that are either a little, or far, away from the normal foreign-tourist haunts.  You're more likely to find it useful when you get into an area where you simply don't see any other Western faces, but those can be the most enriching experiences, and where you may find some of the best bargains and most interesting foods.  Also, in those areas, there's commonly (but not always) much less difference between the merchant's initial asking price and a reasonable final agreed-upon price.