Oy, change the first part of the above post.
Fontana station is the one that the Omnitrans 61 goes to, but it is not the nearest station to ONT on the San Bernardino Metrolink Line; Upland is!
(OK, maybe Rancho Cucamonga might be the same distance, but to go there involves heading east, plus one can travel quickly from ONT to Upland station on Interstate 10.)
So, follow
these directions to get to the Metrolink train instead, then follow the above post from L.A. Union Station to Santa Monica.
4.5 miles, 7 minutes by taxi from ONT to Upland!
P.S. From S.M. to Venice, just take
Big Blue Bus 1 or
2
Be sure to get your free Blue Bus transfer from the driver when you board route 10 in L.A.