I would not limit your son to one team or another. If he wants to play club, be sure to hit 4 or 5 tryouts and talk to the coach about the schedule for the club. Some clubs practice much more than others (fall, winter, indoor, etc.) Some clubs do fall and winter leagues as well as spring NPYLL. You need to find the one that meets your level of commitment and your kids dedication to the sport.

At the very least I would recommend attending:

Crabs: www.baltimorelacrosseclub.net - starts 8/17.
Annapolis Hawks: www.annapolishawks.com - starts this weekend.
Baltimore Breakers: www.breakerslacrosseclub.com - starts 8/17.