I like La Mesa, but I grew up there. It has some of the places that many of us like to visit near the downtown which is quite walkable: including a Cost Co and a regional shopping center. It has a huge hospital complex- Grossmont Sharp if that matters to you. I cannot speak to the schools because the one I attended is now a charter. It was a great place to grow up, but that was a long time ago. Mt. Helix has some very nice properties and there are a lot of post moderns mixed in with some 1920’s style craftsmans all around the older downtown section of La Mesa. The trolley runs through the center of town.
On the negative side I agree with the comments about the Police Dept. being on the CS side and the City voted in a tax increase to balance its budget. Will it become hip? Who knows? It has quite a few antique shops and it started the local Octoberfest many years ago. It does not get as hot in the summer as El Cajon, but it is hotter than North Park. Maybe you should rent there and see if you like it.