pm me if you want some info, but where are you getting tanks filled to 3500 psi?
as for places, straight off of the commerical pier, and out towards the balls n and s of PE are some good places to start.
also i don't think i would swim till i only had 1000 psi and then expect to swim back. 1/2 your tank on the way out and 1/2 your tank on the way back in.
Currents vary, last weekend there wasn't any current in 80' and the vis was ~ 60'. friday the 30' stuff had a 2 knot north current running across the top of the reef. an easy way to check the current is to see which way the anchored ships outside the port are pointing. this will also give you an idea how strong the current is.
may i highly suggest having a dive buddy or two if you are not experienced diving without a dive master.
I had the pleasure of towing a friend back to shore from the 30' ledge when he cramped up and could not swim by himself.
last idea if you are going to be doing any surface swimming. pay attention to the boats. there are alot of idiots that run around in the shallow water and they are not going to see you. don't have your flag tied to you, and carry a big one so people might have a chance to see you.