Upvote:8
According to the Mexican consul in San Francisco, it looks like you should be able to use your US visa for tourism entry to Mexico as long as it's still valid:
With the purpose of facilitating and promoting travel to Mexico, effective May 2016 all those foreign nationals, regardless of their nationality, visiting Mexico for tourism, business or transit are NOT required to obtain a Mexican visa IF they hold a valid (non-expired) Visa or Permanent Residence of any of this countries: United States of America, Canada, Japan, United Kingdom or Schengen area (European Union).
You may wish to call the nearest Mexican consulate to you to double-check this advice since it is from 2016 and also since your US visa is only valid for transit. I doubt the fact that you are not using it for transit on this visit would be relevant but perhaps you should ask about that too. I would also print the page from the consulate to take with you in case of any confusion.