Hawaii is also more than 2000 miles away from the mainland--Honolulu is farther from Los Angeles than LA is from New York City. Puerto Rico is closer and at a similar latitude, but the immense infrastructure costs of a permanent multi-use launch facility put a fair premium on something that you can easily ship to, and it's much faster and cheaper to ship rocket components a thousand miles by rail than two thousand by sea (plus another thousand by rail if the components are built inland somewhere like Ohio or Missouri).