Check them on online to see who is selling what your after as some prices vary, usual B&H, Andorama and the are a couple of other main stores around, if you are there for a while you may be able to get equipment shipped to you which is cheaper from other stores. Just remember to take into account state tax and sales tax is its applicable as it varies from state to state.
Walmart can sometimes be a source of bargins and there is a Costco if you have a card.
Might help others advise if you say what you are after.
Also try POTN site as its mainly USA users.