it is $20 for visitors to park at the onsite hotels for the day.
like Damo said, once you check out at rph, your room key is invalid.
it would be cheaper for you to leave your car at rph and use the water taxi to city walk, switch to hrh water taxi.
this is a new question for me.
if you are at rph and check out, you are allowed to stay and use the facilities, such as the pool and pool shower room at that hotel until you depart from the hotel that day.
if you check out and go to another pool, you would have to show your room key for the towels.
but then, if hrh doesn't scan the cards, you would not have any issues.
you would receive accurate information by calling the hotel now if you need to know in advance.
i don't know anyone that decided to pool hop after they checked out of the hotel.