A 15 minute city is where everything is available to you within 15 minutes walking, biking, or public transit.
I know Mexico city fits this bill. Playa del carmen as well.
PDC I’d rather avoid. A bit too party tourism, dangerous I found.
Vallarta I’ve been too and almost fits. I enjoyed there.
Mazatlan, Sinaloa has a malecon (boardwalk) that’s 18 km long with plenty of restaurants and shops along the route. You can walk, ride a bike, take a bus or pulmonia (an open air vehicle similar to a golf cart). Enjoy the magnificent ocean view.
Centro in Mazatlan would fit the definition. With just a pedal bike I was able to get everything I need (except for good surfing, lol). Great local markets, great farmers markets, transit system was quite good too.
I could run along the Malecon and up through the hills toward the lighthouse, then up to the top. To find running elevation so close to the center of a city is very unusual.
Internet was pretty good in most cafes and the “capacity for excellent was in place” at rental apartments. This is a nice way of saying you could have 200GBs every day but the power could go out or the internet might drop for 20 minutes or so. That said, uptime was around 90%. I had no problem working but lengthy Zoom calls sometimes dropped.
Speaking of rental apartments, we found places from 12000 pesos up to 25000 pesos. It was a little cheaper that other places we looked and the density of the grid pattern means there are hundreds of options within a 15 min walk.
It’s one of my top places but very little surf culture and support, and the breaks were not logistically accessible without a car. And my life is better when I surf.