I'm not sure what you like to do, but a few years ago, on a whim - I bought tickets to a concert in Austin,TX at the OneWorld theatre (we were living in Boulder CO area at the time). I'd never been to Austin, and we went for just three days...having nothing planned other than the concert.
Really enjoyed it - wandered around funky streets (South Congress I think it was), visited the presidential library/museum, and so on. We didn't go *during* the SXSW festival - I think we were there the weekend before it started, but it was a fun time because there was a lot of musical energy gearing up for the upcoming festival. I remember driving around this beautiful lake area as well, looking at the hills. Got to see the Whole Foods headquarters (just for fun, since we didn't have any major plans). Walked all through the state capitol and just wandered around all over the place at our leisure. I would definitely go back there if I had the opportunity.
It was March when we went - and pants/sweater and trenchcoat was just fine for that time of year. It wasn't cold, but it wasn't "summery" either, if you know what I mean. I would say that March, April or May would be good months to visit Austin.
Alternatively - what about Boston (area)? Thoroughly enjoyed a trip there too (although it was a business trip for my husband). Ended up staying at an unexciting chain hotel, in a quaint suburb (Marlborough), near his work ...but we drove all the way to Marconi Beach on the weekend...just *fabulous*. I loved that drive up the Cape and the amazing beach. Found little lobster roll sandwich stands along the way, as if they were hot dog carts or something Marconi beach is one of the most breathtakingly beautiful beaches I've ever seen. Just incredible, and well worth the beautiful drive up the Cape. September is a beautiful month for this idea (imo). This is probably a little far (flight-wise) for just a long weekend though.
These two suggestions aren't anything like Vegas though! I'm just suggesting places that maybe most people wouldn't think of at first for a nice getaway. Lots of people think of Vegas, Hawaii, San Fran, NY etc. but not so much Austin or even Cape Cod.
eta: I have another one....Newport Beach! Nice in September. Do you like jazz at all? How about the jazz festival at Newport Beach?? (ack, now I've gone and given myself a bit of a travel bug...)
http://www.travelcostamesa.com.....-festival/
I'd recommend staying at the Hyatt Newport Beach if you were going to the jazz festival. It's an older hotel, but still wonderful.
http://newportbeach.hyatt.com/.....x.jsp?null
PS - the Hyatt Newport beach hotel is in close proximity to Fashion Island shopping center too...
http://www.shopfashionisland.com/Search.aspx
