Not only is pool hopping allowed, it is encouraged.
The nice thing about having a cabana at the Hard Rock is that you can use it as "home base" for your park day. Since the Hard Rock is such an easy walk to the parks (about 5 minutes), you can go to the parks, come back and swim, go to the parks, swim, parks, swim, etc.
I see you are going in August, so you will probably not want to be in the parks during the hottest part of the day. With FOTL, you are not going to have to worry about lines, so you can ride at your leisure. When we go in the summer, we get the cabana, check in early morning, leave and go do the parks for a few hours. Come back at lunch time and have lunch in the cabana by the pool and swim during the hottest part of the day. Then change again in the cabana and head off to the parks for the afternoon. Then come back and finish out the night again in the cabana. It works really well during those hot, sweltering days in August. Especially since the Hard Rock is so close to the parks that going back and forth is very easy.
Also, be advised that you will still need the Aero bed for your 5th person in the deluxe room at the PBH.
Have a great vacation!