We've just ridden through Mexico - I totally agree that the speed bumps were, without doubt, the most frustrating thing about Mexico.
However, we still chose to take the old, libre roads - There is so much more to see and experience by going through the little towns, and villages. The roads are more curvy, more interesting, more fun, and the fact that the suicide dogs could sprint out at any time adds that element of excitement.
I agree that if you are in a hurry, take the toll roads, they are smooth, direct and fast. If you have time, take the original roads, and ride round the lorrys clambering over the bumps.
All the best!