[UPDATE, July 9, noon: there are actually TWO craft beer festivals next weekend. Your cup runneth over! See further down the post for details of the Tijuana-centric festival.]
If your idea of Mexican beer is Corona (lovingly known in this house as meados de gato), Tecate, and Negra Modelo, you've got to get educated. Baja California has been spawning craft breweries at a rate not seen since North San Diego County, and the old days of beer-flavored soda water are ending.
Forty brewers will be exhibiting their wares at this weekend's Baja Beer Festival; entrance will cost US$5, which will include a commemorative glass and tastings. If you like what you taste, you'll be able to buy bottles, which will cost anywhere from US$2 to US$20 each, depending on size and contents. (Mexico, as you can probably guess, is a lot less neurotic about alcohol sales than the United States.)
The festival will be on Avenida Revolución between 7th and 8th Streets
(in front of the old jai alai palace) from 2 p.m. to midnight Friday,
July 13 and from noon to midnight Saturday, July 14. It's 15 minutes'
walk from the border–park on the U.S. side, ignore the taxi touts when
you cross through the gates, and follow signs toward the centro. Head down Revolución and you'll see the festival.
What to drink? All of it! I love Zesde and Rámuri, Frontera and
Insurgentes, but try them all–I haven't had many bad craft brews in
[UPDATE, July 9, noon:] If that's not enough beer, the Tijuana Beer Fest will be at the same time in the parking lot of the Caliente Casino (the Hippodrome) on Blvd. Aguacaliente. It's a short and cheap taxi ride from downtown. Admission there is US$10, with a concentration on beers actually brewed within the city limits, but there will also be live entertainment including a Guns 'N Roses tribute band and a DJ playing Nortec Collective (but not actually Nortec Collective themselves–damn!). More beer, more samples, more bottles–and then you can get a taxi to take you straight to la línea, no walking required.
A note to you young-uns: you can drink at age 18 in Mexico, but you can't bring any back north of la línea if you're under 21–and yes, they enforce it. Those of legal age can bring back up only one pinche liter (33.8 fluid ounces) of liquor, thanks to California's ridiculous laws.