Is it safe to drink the tap water?

No. Only drink bottled or filtered water.

Generally, no. Parking in the beach zone is extremely limited and expensive. Bikes and taxis are easier.

How to spend 4 days in Tulum

Spend your first two days exploring the Tulum Ruins and nearby cenotes to beat the heat, then dedicate your final two days to the beach clubs and town center. Rent a bicycle for the hotel zone to avoid expensive taxis and traffic gridlock.

Secure your transport. Do not rely on walking. Rent a bicycle for $10-15 USD per day or use the local 'colectivo' vans if you are traveling between the town and the beach zone.
Beat the crowds at ruins. Arrive at the Tulum Archaeological Site by 8:00 AM. Ticket lines grow significantly by 10:00 AM, and the midday sun is relentless.
Pick your cenote strategy. Visit Grand Cenote or Cenote Calavera before 9:30 AM. These are popular and become crowded with tour groups by midday.
Navigate the beach zone. The hotel zone is a single road. Use bicycles to move between beach clubs to avoid the notorious Tulum traffic jams.

Is it safe to drink the tap water?: No. Only drink bottled or filtered water.
Should I rent a car?: Generally, no. Parking in the beach zone is extremely limited and expensive. Bikes and taxis are easier.