Very popular....as you mentioned the HEB center is one of the best in he state and Corpus has a LOOOOOONG history of having excellent players. Many top Texas Jrs are from the area and the Premier Academy based at HEB is good.
Good number of Seniors that live in the area as well as some military - but Corpus a good size city.
Add to that the Valley is close by and again has a strong history in tennis with many of the Valley schools on he HS and college level being quite strong.
HEB also hosts a big time NCAA D1 tours evey year and has for years - the HEB ctr has a show court that has like 2600 seats.