Well don't worry, as long as you spend your money in the US you are WELCOME ! it is different if you want to earn some money
It depends more of how long you'll stay there, you might be considered as a tourist or if you stay longer than 3 months (can't remember if it is 2 or 3) you'll need a visa but ... spending your money they'll let you in without any problem ... best is to call the embassy. Good luck !
