You do not need to attend the play to attend lunch (or vise versa).
El Fenix is in the southeastern corner of Garland Road and N. Buckner Blvd. (facing Buckner).
(I do not know how long the $2.95 Margarita special will be going for - it may be over by the time we meetup for lunch.)
Hungry yet? Hmmm, I may need to go check it out before May 10! ;-)