My name is Ernest and I own DJ Masquerade, thank you for your question. The Alamo is a historic location and I am sure there is a lot of red tape and clearances you should call first and check on all the do's and don'ts here is something I cut and paste for you to research your question
Address: 300 Alamo Plaza
Directions: NW of the Riverwalk Mall, downtown
Good Luck from DJ Masquerade www.djmasquerade.com 210-377-DJDJ(3535)
You cannot get married in front of the Alamo. You can get married on the sidewalk in front of the Alamo, but not on the grounds itself!
There's always Marriage Island or one of the Missions!
Here is a great blog from a couple that visited many different venues in the Austin area. They even created a top ten list! The couple ultimately chose Memory Lane Event Center as their favorite. Hope this helps.
Click on each tool to see a sample.