Car rental

My wife and I will be traveling to Puerto Vallarta next week. I see that renting a car for a week is pretty reasonable ($125). Is it extremely difficult to park and drive around town? Or would you not reccommend it.

Also considering going out to the Four Seasons, Nueva Vallarta and Mismaloya while we are staying at the Marriot in the Marina

Yes it is somewhat difficult to drive & park in El Centro (downtown). Very busy & crowded, many one-way streets, local busses, taxis, etc. But you might enjoy having one for those trips you mentioned north & south outside of town on the highway.