Like the others here, I'll give the nod to Albert Coffee, an archeologist whose tour of Cañada de…read morela Virgen I booked through TripAdvisor (about $60US per person).
For reasons explained but not retained, one cannot just take themselves on a self-guided tour of this pyramid and the structures that surround it. Albert Coffee is one of the people authorized to guide you and he does so knowledgeably and efficiently.
Any tour of this pyramid will have you coming to the site via shuttle then taking another shuttle to the nearest possible point. From there, it's about a 1 mile walk, moderately uphill, to the entrance to the site. You'll leave by walking the same 1 mile portion of road in reverse. Alfred Coffee arms you with a bottle of water, most appreciated.
You can bring nothing else with you as those who run the site want no trace left behind. So travel light, as all bags, fanny packs, and day packs must be left in the shuttle you arrived in.
The whole experience, start to finish, ran 5 hours, and was interesting. I've been to both Teotihuacan and Pompeii though, and there's a reason you have heard of those and not this. Relatively, this pyramid was only recently discovered, is evidence of a much smaller civilization having lived here, and there's presumably a whole lot left to be revealed.
The location - seemingly the middle of nowhere - will leave you wondering what else is out there still unknown. There's likely a lot more even at this site but visible excavation appears to have ceased for now.
Still, if you enjoy visiting the structures of ancient civilizations and harbor an appreciation for Mexico's willingness to allow you to climb all over these structures, Cañada de la Virgen should be on your checklist. The tour departs from San Miguel de Allende.