shipping luggage

Hi! I'm going on a repositioning cruise which ends in San Juan. Found a terrific airfare to a different city from my own, but with a change of planes in my city. The plan is to get off in my city and just not use the second plane. Since my suitcase would go on without me, I'd like to ship it home ( should be only one fairly large suitcase- I'll keep a carryon with me) via US Postal Service, UPS, Federal Express or whatever else is available. Any idea where in San Juan I could do this ( that would be open on a Saturday), hopefully at or near the crusie terminal or airport? Thanks for any help you can give!