Here is the addy for the Discovery Center, You can map it out.
http://tinyurl.com/37e58n
Big Bear Discovery Center
40971 North Shore Dr. (Hwy 38)
P.O. Box 66
Fawnskin, California 92338
(909)866-3437
There are several ways to go up, 30/330, 18, & 38.
The 30/330 is the shortest, curviest, and busiest.
I like the 38 through Redlands. A little longer drive, but less curves and traffic and you get to drive the speed limit (or a little better :spin1: )
The 18 through the High Desert is probably not the best route for you coming from Ontario, but you would go up the 15 to Bear Valley Cut-Off (through Lucern Valley) and up the backside to Big Bear.
I hope this helps a little.