5th Ave is THE street in Playa. It starts at the pier near the small airport which also is the terminal for the Cozumel ferry. It stretches north for about 17 blocks to 34th street. (note the east-west streets are all even numbered 2,4,6, etc. And the north-south avenues go up by 5’s 5,10,15,20, etc.
The street seems to get a little nicer as you head north from the ferry terminal. The shops change from cheap trinkets to bars to nicer restaurants as you go north. The prices of things also seem to go up a bit and the nighttime noise goes down.