how quick a trip? That would make a difference. If a long weekend or something, I'd add Buffalo for Niagara Falls.

We had them for years. Given hurricane season I’d say:
Hawaii
Cabo
Aruba
Arizona or Las Vegas (for national parks) if you can do late like October

We went to Seattle and got on an Alaskan cruise. My favorite vacation ever.

Portland, ME- Tucson, AZ, Austin, Chicago, hawaii

You are going during hurricane season so keep an eye out for that. We just had a great trip to Belize (southwest has direct flights some days from bwi). There is great snorkeling not too far from the airport.

Los Cabos (but head up to Todos Santos)

We have had two SW companion passes for years for our family of 4 and some of the best places we have gone to were: Costa Rica, Puerto Rico, Cancun, Aruba, Denver, Seattle, Utah parks road trip (into Vegas and out of Salt Lake), New Orleans, Marco Island (into Fort Myers), Finger Lakes (into Rochester), Hawaii (Maui, Big Island, and Kauai).

Seattle or LA are two great options. I would do Seattle and go to the San Juan islands

Grand Cayman

I'd start with where Southwest flies nonstop:

https://en.wikipedia.org/wiki/Baltimore/Washington_International_Airport#Passenger

They fly to San Jose and Liberia in Costa Rica, but not every day of the week- I think Liberia is Saturdays only- and may actually be winter only. They also fly to Seattle and Portland, 2 great options in summer.

Long time SW Companion pass holder here, Denver and go to the mountains, Vegas and head to various national parks, Portland for a road trip through Maine/New England, Albuquerque and go to Santa Fe, Spokane and go to Northern Idaho (we love Sandpoint). I could go on and on. Happy planning!

I qualified for a Southwest companion pass through a promotion and would like to take advantage of it for a quick trip (or trips) with my spouse. It has to be used between August and October and I'd like to travel somewhere we wouldn't ordinarily go. Right now, we're thinking Puerto Rico or Turks & Caicos, maybe New Orleans, but are there any other cool places Southwest flies that might be enjoyable for a couple?

We'd like to get away from the East Coast and aren't limited by weather considerations (hot or cooler is fine) or activities (urban, beach, mountains, lakes, are all in play). I guess the only qualifying is something a little romantic and good for couple time.