easy off and on I35 and plenty of parking...probably a park and grab for some and an evil cache for others. 
congrats to rbarron794 for the ftf!
i drive by this lot at least 20 times a week. some weeks probably a few times more and others a few less. there is a small building on the lot and i've never known what it is. a good friend of mine who is an alvarado local says it used to be a gas station and maybe it was but it looks like a ticket booth for a football or baseball team (however, there is no room for either of those types of fields here). it also looks like it could have been a small bus station. my buddy assures me it was a gas station so i guess i oughta go with her expertise and change the title of the cache but for now i'll leave it like it is.
i checked the coordinates at least 25 times and they were very close--sometimes they even matched--so hopefully your gps will lead you right to the spot you need.