^Mom and sib! Darn autocorrect.

went to / had a couple of these as a kid, and we always got suites--one room for mom & sibling, and another with 5-6 girls. Very fun.

We have both hosted and our daughter's have attended pool parties at Embassy Suites (or Residence Inn) on Leesburg Pike. Adjoining suites, mom and sub slept in one room, 2 girls in living room of that room (pullout), and five or so in adjoining room. The girls swam, ordered pizza to the room, then watched a movie and had microwave popcorn and candy (that I brought). Huge success. The hotel does have a bday package.

Second the suggestion for a county or city pool. For example, the Rockville pool is really nice, with plenty of tables and lawn space. And entrance fees are only $6 per person. You can get at least 10-15 people in for the price of a hotel room.

Oh come on, people, there's no way any other guests or the hotel management are going to notice 30 teenagers having a party in the pool and hanging out in one room.

If you wanted to be shady about it...5.

Anymore than that and you will likely wind up being kicked out by the hotel (and rightly so).

Ask the hotel.

I went to / had a couple of these as a kid, and we always got suites--one room for mom & sibling, and another with 5-6 girls. Very fun.