No special access issues
The Mirador del Montsec crags require lengthy drives along un-surfaced tracks in order to reach the parking areas. As stated in the approach information, in dry conditions these are okay to drive in a normal (non 4x4) car providing it has reasonable ground clearance and the driver is used to rough tracks. However, climbers visiting from abroad and using a hire car should note that damage to vehicles driven 'off road' is never covered in the rental agreement.
After prolonged wet weather, nothing short of a true 4x4 will get you to your objective!