See if you can fly to Reus, Ryanair and a few European budget airlines go there, and it's literally a 10-15 minute taxi drive away from the park. If not, it's an easy train journey from Barcelona by train.
I have stayed at the Gold River hotel and actually really liked it. Not sure about the PortAventura hotel. The theming was really nice and it has its own entrance into the park, but it wasn't really possible to go to other hotels in the evenings (like I normally do at Europa or Disney).
I think if things go your way you can do the parks in two days, but the operations are very unreliable, so it depends when you are visiting and how much time you would normally spend eating, watching shows etc (some of the shows are good), so maybe 3 days if you aren't on a tight schedule and you're not likely to visit again for a while.