We did it a few years ago (2019) in late Dec. and returned late Feb (2 months). Went down to where the monarch butterflies migrate too; past Mexico city.
Overall, no issues at all. It does take some planning but that's more for logisitcs of crossing the boarder and getting a permit.
No issues finding places to camp, campgrounds, etc. We used ioverlander a lot and a few books/guides. We have a diesel and no real issues with that either. We did quite a few "off the grid little towns, campspots, etc.
Tolls aren't an issue but yes, I bet we spent $372 on tolls but feel that they were worth it. We went down the gulf side, then cut over at Lazaro Cardenas towards Mexico City and the Monarchs. We then went a little further south then turned north. Eventualy we turned west again (at Durango) towards the coast and back up the way we came. The tool roads from Durango to the coast was expensive (toll wise) but so very cool. Lots of tunnels, high in the mountains (we had some snow even) and was worth it (it was very pricey though; looking at my notes I don't say how much we spent but I'll bet it was around $70-ish).
I have copious notes, my ratings, days we spent at each place, etc.
On the tolls. Some times they are free. The attendents are gone or something and then you just drive through. I think the attendants might have had some issues (strikes) when we were there though and for a while there was a gas shortage. Since we had diesel, we were never affected. Driving can be an "experience" and sometimes you just go for it. Signalling is different down there and what turning signals mean on cars; can mean I'm turning or "you can pass" or something else. That part takes time to understand as you obviously don't want to pass if they are turning.... Roads in general were great and why we took the tolls roads (but sometimes we wondered what the toll was for as it wasn't for road maintenance).
Anyway... I have so many notes but you can find some awesome beach camping, little towns, etc. We tried to pull into one's that looked great; sometimes to spend the night, sometimes just to check it out. There are a lot of places we'd love to go back too. One of the places we stopped on teh way down, we ended up staying multiple nights and then went back there on the way home.
I'm reluctant to state where they were for a number of reasons; would get overrun or they could have changed and wouldn't want to suggest a place that has changed over the last few years.
Be sure to have copies of the documents you need for border crossings and permits as it'll speed up the process. Know where you have to go (where we crossed the TIP permit was 30 miles? down the road). Also, get Mexican insurance!
Have fun.
Tricks for attaching gear, etc. to the outside of an ATC?