I agree that you do not have to take a class, but we did and it was so much fun. Classes with your baby can be a fun thing and so we chose sign language. I searched on the internet and found a lot of options, it is just hard to find an option that fits location and time. Some educators will do a private class for you and your friends.
I took two different ones. I took Baby Signs from Kristy (http://www.babysignswithkristy.com/index.html) but her current classes are in Coppell. I also took from Kari who teaches through soundsteps kindermusik. (http://kinderweb.soundsteps.com/index.php?display=Classes...) I think her classes this semester are during the day so neither of those will work for you.
I would just search online. There are several kindermusik "franchises" that offer sign.
Some other sites are:
-Sign to me Classes in Texas http://www.northlightcommunications.com/region.php?region...
-Wee Hands Classes http://www.weehands.com/weehands_with_tammy.htm
-Kindermusik class locator
http://www.kindermusik.com/locator/locator.asp
Another thing to look for is the Signing Time series. It is currently playing on PBS every Sunday from 6:30-7 am. They are great videos and teach a ton of signs. I have my VCR set to record them every week.
There are also online signing dictionaries such as http://www.aslpro.com/cgi-bin/aslpro/aslpro and
http://commtechlab.msu.edu/sites/aslweb/browser.htm
http://www.mybabycantalk.com/
http://signwithme.com/002_browse_signs.asp
I hope that all helps.