Can I mix LL and LR parsing?
Using recursive descent in combination with an operator precedence variant for expressions is a very common approach. You might also want to search for Pratt parsing. 

An older, now uncommon technique which combines LL and LR parsing is "left-corner" (LC) parsing, which should also be easy to search for.

In practice, the existence of easy-to-use and efficient LR parser generators makes all of these less powerful techniques much less useful. LC parsing was pretty well obsoleted as a technique with the discovery of the LALR algirithm.