Local Little Leagues play until June. Call local District 19 to discuss which league plays in your area. Good news in SA is if local league doesn't fill your schedule with 2 ballgames a day M-F and 5 on SAT, then go to other nearby leagues to fill up to capacity. Find the best teams and talk to COACHES, and they will know how to get you in contact with local SELECT leagues. The local ADULT umps can also provide info on HS and select summer and fall baseball. The District 19 umpires hold clinics in JAN/FEB/MAR across SA and those individuals (one in particular) are AWESOME, the best in the area at any level (NCAA and PRO ballers included). LL PAY every 2 weeks. Local CYO leagues also exist.
http://www.salittleleague.org/
Two main HS ump groups are TASO for HS Varsity and some JV. Good luck, and believe half of what you hear there (Every person I talked to thought he was the greatest). Those who don't like the politics or don't get JIGGY with the BS training from JOE SMITTIE prefer HS JV with another group.
http://www.southtexasumpireclinic.com/
They hold a clinic the week before the Superbowl and baseball season begins the week after it. A very good value comparable to PRO school. JV season is drawing to an end but SA ISD will have a JUNE M-T league. I prefer this smaller group because you can get all the games you want w/out the politics. HINT: There are not enough UMPS to cover all the baseball. You may work games with partners or w/out. Must keep HS schedule because payday is 1 to 2 months later. I have never had a problem I couldn't contact somebody to resolve for me. Folks are great.