Short answer: you won't be going to Houston if you're in PLC this summer.
Long answer: After the 3rd or 4th week, you will get approximately 24 hours of liberty, from Saturday afternoon through Sunday afternoon/ evening. However, you may need to come back at some point during that time for fire watch. If you're the duty platoon on liberty, your platoon will have a few extra watch duties, and you will be restricted to the Quantico base, which basically means that you can go into Q-town but not much else. If you're not the duty platoon, you are still restricted to an 80-mile radius from Quantico, which will let you go to DC or Richmond, but not to Houston.
I'd plan on setting aside a good time to give your buddy a call after the wedding.