Where should my gf and I go for the one week of spring break?

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Where should my gf and I go for the one week of spring break? We are white Americans in our early 20s and, though adventurous, would like to stay safe (which means we would like to not be stuck on a beach resort the entire time, we'd like to get out and enjoy some local culture without being tourist-y while remaining safe).
We are both /lit/ and into the arts.

We have free guest passes for SW airlines, so if you want to look at their potential destinations you can. This is what limits us most.

Otherwise we have narrowed it down to the following, which are all places neither of us have been:

Seattle: A major pro is that we have friends that live on Pike, so we have a free place to stay. Not at all worried about safety for this one, obviously.

Mexico City

Jamaica (Probably Negril and possibly a trip to Kingston, but open to other suggestions)

Costa Rica (We'd like to see the rainforest above all else here)

What can you tell us that will persuade us to visit one place over another?
Side note: We live in Milwaukee, and have never been to the east coast either. Boston interests me, but if we stay in the US we'd go to Seattle to visit our friend that moved out there 6 months ago. I also have a cousin that I'm close with but don't see often that lives out there.