With only two days in Mexico you are sort of limited in what yo can do but there are some options I can suggest for routes.
If like Lone Rider says you " go shallow" you could just go to Brownsville and follow highway Mex 2 along the Rio Grande Valley with a number of side trips, to Ciudad Acuna and cross back into Del Rio Texas. Don't laugh , if this is your first ever trip into Mexico it can be a pretty instructive ride and with all the sightseeing and town investigation it can easily take two days to cover this distance, done it. It will be unquestionably different than Texas, REAL MEXICO. You will not need to bother with the temporary import papers and fees nor the tourist card as you can do the entire trip within the frontier zone. And you do not need to run along the river bank because the zone extends some 50 km inland or more untill you come to the Aduana Inspeccion station somewhere, so you can legally explore alot , like to Valle Hermoso, Bagdad Beach, or take Mex 57 to Allende and the back to Cd.Acuna via mex 29. Lots of stuff to see , and you can drop into one of the big Soriana stores , or Gigante, and some magazine stores to find a Quimera or Guia Roji road atlas so that you can plan future trips.
If you want to "go deep" think about the trip from Nuevo Laredo to Monterrey stay there for the night , then east to Reynosa, Matamoros and back to Texas. This too can easily fill two enjoyable days with comfortable distances.
For the megadeep two day ride think about entering at Eagle Pass to Piedras Negras , then down Mex 57 through Allende where all the customs paperwork has to be done at the "Garrita km53", after which you can drive steadily all day with side trips through the downtown of the cities along the way(Nva.Rosita, Sabinas, and Monclova) This is high desert country. If you pace yourself you can reach Saltillo by late afternoon and spend a night there. If along the way you decide you are running out of time there are connecting roads east to shorten your trip :e.g. from Monclova east to Candela then Anahuac back to Laredo, or from Castanos on Mex 57 you can take a shortcut southeast directly to MonterreyIn the morning you can either take Mex 40 east to Monterrey or if you like a chalenge on your cruiser bike take Mex 57 east out of the city east to Arteaga then split off onto the small state highway east into the mountains This road is real scenic sometimes a bit rough but you will remember it forever.Via Los Lirios and a short side trip to Laguna de Sanchez , then over the top and down past Horsetail falls it winds up on Mex 85 south of Monterrey. From there either go back to Monterrey and Mex 54 east to Miguel Aleman and Texas or go south on Mex 85 to Montemorelos and then east to Reynosa on Mex 35 and Mex 40 .All of the roads are good, personally tested, and the scenery is varied., enough Mexican towns to get a sampler .
Again , for the Mega -two day ride you will have to pace yourself to not get overtime , but the total distance is only about 660km , quite possible to do in two days , with ample time to enjoy .
Hotels are all over and security is not a problem , just make sure you check into one where you can park the bike in the parking garage, the lobby,or the atrium and you can wander around the plaza al evening, check out the restaurants .

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http://advrider.com/index.php?thread....207964/page-5 then scroll down to post #93