I have a center unit in a townhouse so I can't do a mini split. If I had a end unit, I would. I have heard portable ac's aren't great. However with a 1 car garage and only 230sq ft. I think a 14000BTU unit would hopefully do the trick.
I have the option of running the duct work from the townhouse HVAC to the garage. The garage is only 1 car, 11.5ft by 20 (230sq feet). Its a center unit townhouse and garage door is insulated so it not super hot in there. I do live in FL so it is humid. I will be using the garage as a gym...