The Mex 190 does not touch Toluca , Mex 55 does go south from there. But when you mention the state Hiway 4 you are definitely on the right track for getting to Cuernavaca . Best go east from Toluca then south on 36 to pick up 4 south in the heavily industrialized valley basin. But then make sure at Sta Martha you turn off 4 to go EAST on Mex 106 across the wooded mountains and the Lagunas de Zempoala .. Screen grabs off maps. me That will take you onto Mex 95 about 11km north of Cuernavaca . Pretty crowded valley country there too . From Cuernavaca. it is a matter of going east on the 138 and hooking up with Mex 160 southeast to Izucar de Matamoros . And THAT is where you finally join Mex 190. Hotel towns are spaced about every 50km to 80km - or less - to Oaxaca , You will love that road . It has well maintained surface , light traffic , sweeping curves over the ridges, great views and spots where it will be a preview of how mountainside farming in the Guatemalan highlands is done . East of Oaxaca valley , past Mitla it does indeed get sparsely populated , hotel towns are spaced farther apart but reasonable range of maybe 100km . Oaxaca to Tehuantepec is a nice day of easy calm riding . No worries.