Please, for the love of everything that is holy, please bring Verizon FiOS to Key West, FL. Comcast has a choke hold on this place, and their internet connection is spotty at best. I'm paying way too much for way too little.
Cost is a relative term. Unfortunately it doesn't look like Verizon is going to be expanding either the DSL or FiOS network very much in the near term.
That leaves you with only two other choices. Boardband via Mobile Phone Network like Verizon Wireless mobile broadband, (Key West appears to have Verizon 4G LTE coverage) and Sat based Internet providers such as WildBlue, Starband and HughesNet.
Figure you are going to probably pay more than you are now, and mobile broadband, and Sat based systems usually come with download limits which if you like to download full length feature films, are going to be a problem.