While writing my guidebook, I had a tough time finding information for lesbians, so I was happy to discover the following English-language website while net-surfing:
http://www.machamexico.com/It has helpful information, interesting articles (the most recent about lesbian mothers in DF) and useful links. It looks good and is easy to use.
Another tip is the weekly magazine
Tiempo Libre which has a GAY section that lists events for lesbians (like 'lesbian night' at otherwise male-only gay bars)
The recommendation in my book (www.eventoslesbicos.org on page 100) seems to have degenerated into a sex-for-sale website. It will be removed in the new edition.