Wow, thanks for the replies!!!
I think I'm going to go with the LM2596. I can't buy premade boards because the regulator has to be part of a bigger board.
Now a follow up question. I don't think I'll be going beyond 2A. So, if the LM2596-5.0 has 80% efficiency, and I'll be drawing 2A max, will it always dissipate 2.5W??? I calculated that like this:
output of 5V * 2A = 10W
efficiency 0.8 so, 10W/0.8 = 12.5W of input needed for 10W.
12.5W - 10W = 2.5W
My question is, do i still need a heatsink for that?...