Rachio 2 controllers are no longer made, although you can buy them used. Rachio 3 controllers use Weather Underground personal stations, rather than PWSWeather.com stations mentioned above. The main difference, to me, with the 3 vs the 3e is the 3 has more upgraded Weather Intelligence features and future upgradeability, which I think you will want.
To check for personal weather stations in your area, go to Mexico City PWS, then use the map to zoom and move around to your location, to see if there are any PWSs near you. If you’re near a larger city, there no doubt will be, or use the one 5 miles from you, that’s not too bad. But you can see if there’s one closer to you using the map.
Oh, BTW, the only value used from your specific PWS is rainfall; the rest comes from stations in your area, so you’re not losing that much if you don’t have a (close) PWS.
As to not using Flex Daily, hopefully someone from Rachio can confirm or deny that; hopefully they’ve extended their database to include live weather in Mexico as well.