There are some fantastic flight schools in the States, but also some sharks. On my way up to an FAA ATP I experienced both. Ideally, see if you can get a recommendation from someone you know who has had a positive experience, this is likely to increase your chances of not being screwed.
Relatively few US flight schools will 'spoon feed' you the theoretical knowledge that you need to pass the written tests (there is ONE for the FAA private or SEVEN for the JAA PPL) and anyone thinking of heading out to the states would be advised to do sufficient self study to pass those before leaving the UK. Ideally, sit the exam(s) before you go as well.
Once you get out there, the equipment you ACTUALLY need is as follows . . .
i) Terminal and sectional charts for the local area.
ii) A flight computer (whiz wheel)
iii) A square protractor
iv) A scale ruler
You should be able to borrow almost anything else.
So far as instructors are concerned, different people gel better with some instructors than with others. If you feel you're not making progress speak to the Chief Instructor and maybe look at changing instructors.