If you want less hassle, Uber takes 20 mins to get into/out of the center (25 with traffic which is only at rush hour, 8-12€) and 5-7 minutes to Oriente (3-5€). The metro takes a bit longer.
If you check your bags 6 hours before your flight, you have 4.5 hours to enjoy. If nothing else, find a nice cafe and enjoy the scenery.
If you're not *G, plan on entering the security line 90 mins before departure to enjoy a smooth experience.