hi Audie

first english is spoken extensively in thailand and all over bangkok.

there are all sorts of things to do that need no guide and a few where a guide would be helpful, but there are travel agents all over bangkok and you will be innundated with them at the airport when you arrive.
recommend getting out of bangkok if you have that much time if you can. you can do it very cheaply if you dont have much money. (an overnight bus to chiang mai for instance.

but there are tons of things to do in bangkok on your own including shopping at the weekend market, going to see kick boxing, going to the old capitol, etc etc.

you can do much of bangkok's sites on your own. Having a guide is faster and gives you more history, but it's not difficult to see the sites on your own and all have english language info