Memorial Drive and Storrow Drive both have low bridges that frequently snag trucks. So the best route for a truck to the Hyatt Regency Cambridge hotel from the Interstates appears to be:

Mass Pike (I-90):

Take Mass Pike to Exit 18 (East Bound) or Exit 20 (West Bound)
Go toward Cambridge (cross the river)
Follow River Street to Central Square
Turn right on Mass Ave
Turn right on Vassar Street
Turn left at the Hyatt

If you're coming from North or South of Boston, take I-93 to the Mass Pike and then follow the Mass Pike directions. The Mass Pike for a 24' truck (two axles) is $1.25 from I-93 to exit 20.