Thank you! Now I'm thinking of course ... Puerto Rico? I don't know how much fresh water there is, or if there's available and suitable land on the east coast. Are Georgia or South Carolina too far north?
To put some numbers on the "north"ness.
Boca chica is at 26 degrees north, which gives you 416 m/s free velocity (1500 km/h) [1]. The southernmost point of Georgia's coast is at 30 degrees or 401 m/s, the southernmost point of South Carolina's coast is at 32 degrees or 393 m/s.
Actually calculating payload to orbit is more work that I don't really want to do, but you can find someone else who put in the work on this stack overflow question [2], just for different latitudes and a different rocket. 28 to 30 degrees is roughly a .3% change in payload capacity in their model.
You're definitely not the first to suggest Peurto Rico, but I think you have the same problem of there not being enough empty land [3].
[1] https://www.google.com/search?q=%28%282+*+pi+*+6378.14+km+%2...
[2] https://space.stackexchange.com/questions/998/how-much-of-an...
[3] https://www.quora.com/Why-don-t-we-build-a-rocket-launch-sit...
https://newsismybusiness.com/11-firms-interested-in-developi...