I really wouldn't call this an "entertainment PR agency." There's very little PR going on, especially for interns. Interns are in charge of making sure those advanced screenings are packed. If you're a general intern, you'll work on whatever needs to be done and you won't get paid. Be careful with this--you could end up working for the co-ops and other interns. If you're a studio intern, you'll work for a specific studio, and get paid. You have more contact with the publicists in this position, which could be good or bad depending on who the publicist is. But, bottom line, they have very little connection to NY and LA, and there's no room for advancement unless you want to move up from stuffing envelopes to send to businesses, to stuffing envelopes to send to radio stations...because that's pretty much all that happens.
That being said, I really liked working there. While it didn't advance my career at all, the other interns were fun and it was a good time. It's fun to see the movies and hang out, but don't take it thinking it will open doors.