Tim,
Bird is very flat and there are on-the-beach rentals (Worldwinds,
www.worldwinds.net, owner: Don Jackson). They have Gaastra/F2 rentals (all boards are 2002, about 2 months old).
Cline Street offers rentals that you can take with you, but I don't know just what he (Oliver) offers for rentals. If you are a Gorge sailor, you are probably going to want to sail the Bay over BIB, which is *very* flat. There are a variety of launches on the bay, some with decent chop.
If you are looking for flat water speed, BIB will be good for that, though. It's about a 45 minute drive from downtown Corpus Christi.