Welcme to San Antonio. I moved to San Antonio a couple years ago and have found good bass fishing at most lakes that I've been to.
Canyon would be a good lake to go to. I don't think you should have a problem launching at Canyon Lake now that it is full of water. I know there has been construction in the Cranes Mill area and I don't believe that ramp is open. I've recently launched my boat at Potter's Creek and Mystic Shores (County ramp 23) without any trouble.
Dunlap would be another good option.
I fish Medina regularly because it is about half the distance as Canyon from my house. Medina can be a good lake for numbers of 11"-13" LMB with occasional larger bass.
Choke Canyon, Amistad and Falcon are some of the best bass lakes in the nation and all are a reasonable distance from San Antonio.
The recent rains have some of the lakes rising a foot or more a day right now. Check current conditions before heading out. Canyon is already full of water and would be a safe choice for a trip this weekend.
If you waste as much time as I have on this website it won't take you long to figure out some fishing opportunities around San Antonio. The Texas Parks and Wildlife website can also be helpful for learning general information about area lakes. You will find more up to date information on this website though.
Here's a link you might find helpful.
http://www.tpwd.state.tx.us/fishboat/fish/recreational/lakes/