I booked with an OTA called Vibe Adventures, my Xochimilco tour, and you can join any group. So, I would recommend it.
Well, I wouldn't say you don't need to book a tour. Last time I was in Mexico City I booked a Frida Kahlo Museum tour with Vibe Adventures, and it was a cool experience. Best tour guides ever!
a online tourism agency :)
Xochilmico tomorrow 5/8, looking for a group
MexicoCity