Attendance has varied in the 11 years since I started coming to DSFs. The first year I went, 1997 at the Marriott Marquis in NYC, was, I've heard, a record-breaking doorbuster, an estimated 3000 or more filtered in and out during the weekend. (This in addition to the 1000s of other guests and events at the same hotel. A crazy scene for sure !!) Subsequent ones haven't achieved that highwater mark, but those in NYC were usually better attended and sometimes crowded.
The last several years haven't been as over-populated, but the return of Mr. Frid seems to have given things a boost, as well as the proposed Johnny Depp DS film. So it can still be crowded but probably not so much that it should be intimidating.
Plus there are plenty of fine fellow fans to become acquainted with. Just hanging around the lobby during a typical DSF weekend, taking a break from the events, you can meet scads of DS folks, many of whom are on this board. And running into them at whatever restaurants, and maybe end up joining them for a meal or a drink. Or just chatting them up in autograph lines, etc.
Numerous people do dress up in costumes, many on Saturday especially, even if they don't sign up for the onstage Costume Gala usually held that night. And some, if they have lovely gowns or smart ties-and-tails, will wear them to the banquet the next evening as well. (Though one doesn't HAVE to dress up for this, many do.)
Anyway, that's my P.o.V. If you come I hope to meet you. GB.