Upvote:1
Alaska Airlines posts their complete timetable in PDF format. You can also see specific routes. Both include aircraft type.
The PDF timetable uses IATA aircraft codes, of which a table can be found here among other places.
Flights between LAX and MMH are shown with code DH8, which refers to the De Havilland Canada DHC-8 Dash 8 series of turboprops. In the specific route schedule this is shown as Q-400, referring to the model within this series which Horizon operates. So the answer to your specific question is yes, flights on this route are operated with turboprops.