What a fantastic experience!! I would definitely recommend that you visit Monte Alban if you can.
We visited in August 2022 and had read reviews about limited numbers. We opted to book a guided tour to make the transport and entry easier. We arrived at 9am and were able to go straight in. It didn’t appear that visitor numbers were being limited when we left at 12pm as people were still entering. Upon leaving the car park was getting very busy and there was a large queue up the road for cars and buses so I would go early to avoid this!
I would definitely recommend a tour guide - there are some plaques written in Spanish, English & Zapotec but we found out much more interesting information from our tour guide than what we read.
Definitely take a hat, decent shoes, suncream and water. There is a shop at the entrance to buy cold drinks and decent toilets to use too before you enter the main site. There are some areas of shade in some parts to stop and rest.