Can anyone tell me if Riding two up with my wife is a good idea.
In a word, Yes, if you prefer.
You can take pavement all the way to Galeana two up and it is a very, very nice ride with a nice canyon near the end. At a moderate pace taking a few pictures you'll be there in the early, early afternoon.
Map it: Anzualdas, China, Montemorelos, Linares, Iturbide, Galeana
Once in Galeana you can get your room, freshen up, and load back up sans gear and head north out of town toward Rayones. That is the kinda tricky dirt road the rest of the group will be riding into Galeana having gone this route:
Map it: Anzualdas, China, Montemorelos (Lunch), Rayones, (then dirt to) Galeana
If this road is to your liking you will be able to manage most of the roads considered class 1 and 2. There are fabulous routes consisting of all class 1 and 2. And nice destinations (Saltillo, a medium sized city, the waterfalls near Monterrey, a vineyard or two to the west) an hour or two away if you prefer to stick to concrete.
However, there is little to do in Galeana. It's a small town, county seat, and most of what happens is small potatoes. 4 hours and you'd have exhausted everything you could do there, and that includes dinner and bar hopping and shopping.
In my opinion, this ride is best done solo with an adventuring spirit, solo, with the ability to make the trip your own and see what you want to a key part of it. Having someone else to worry about might really diminish your experience. My wife, in an ideal world, would want to go 2 up to Starbucks at best. Mexico has too many variables for me to want to thrust on her.
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Feel free to hang out and lurk as long as you like. However, we would like to encourage you to 
. Yea, the AT will cost a lot more to drop than the XR but it is still fun and spirited. 
