Advice on Mexico
Going across the border with 60 riders in a group is going to take a bit longer than just an individual and going in for only a 30 mile ride into Mexico may hardly be worth the frustration, especially if you intend to start and finish in San Diego.
You will each have to buy liability insurance for Mexico ,which you can do ahead of time, on-line even, but if you were to buy this on the San Ysidro side of the border it could take a couple of hours before your group could ride off.For a single day the service fee will cost more than the actual insurance so you might as well buy it for two or three days, a minor addition. Lucky for you , you do not need to bother getting tourist cards if you stay in the frontier zone for 72 hours , i.e all of Baja .
Why not think about going in early one morning at Tijuana , insured already, and then you could all make your way 110km down to Ensenada, either on the toll road D 1 ( great scenery off the cliffs) or the old free highway and take the whole day to enjoy the sights , and overnight in an Ensenada hotel . Then the next day you could do some sightseeing before taking Mex 3 north back to Tecate-- totally different country and scenery.
As day trippers you can just sail into Mexico with minor delay at customs in Tijuana then the return to the USA at Tecate will leave you free of the long lineups typical of late afternoon border traffic in Tijuana as all the delays are usually for northbound traffic. From Tecate it is then a simple ride back to San Diego.Altogether , a bit longer than 24 hours but at least you have a sampler of Mexico other than waiting at the border and the coastal tourist strip.
This route is all excellent paved highway and there is no danger .Just drive carefully and enjoy.