Pretty sure (like 95%) you have to take the front bumper off. The sensors "lock in" with tabs at the rear of the sensor....Im not sure you'd be able to get enough access through the trim panels for the tow hooks.

Theres some really good diy's floating around on how to remove the front bumper....most of us here can have it off in under 10 mins. (it's really not that hard).

__________________