If anyone has ridden Grand Ave. from West Covina (starting at the 10 fwy) all the way to Chino Hills (where it ends at the 71), i would like to give you a high five or something...
Went for a "short" ride yesterday that started in Ontario, went through Bonelli Park, up into West Covina, down Grand Ave. through Chino Hills then back up into Ontario for a 43 mile loop. It may not seem like much but holy crap it was probably the hardest ride me and my friends have ever done (there's 3 of us that ride together regularly). I believe there were 7 fairly major hill climbs on the route with 5 of them being on Grand Ave. and the other two were on Via Verde i think. Actually, it could have been more like 7 1/2 or 8 hills since the entry into Bonelli park from the east end of Via Verde is essentially another hill climb...
It wasn't so bad really... Went through 1.5 clif bars, a hammer gel, and a pouch of clif shot bloks with plenty of water and gatorade. Temperatures were in the low 60s for most of the ride which necessitated the use of knee/arm warmers, though it did finally get to 70 degrees at about noon. Total moving time was about 3 hours, total ride time was 4 hours (started 9:00am, finished about 1:00pm).
The worst part of the ride: trying to negotiate traffic while crawling uphill at about 6-7mph then having to sprint through an intersection at a stale green/yellow traffic signal (on grand ave. just south of the 60) while your quads are already burning and screaming at you for a break...

Having only two front chainrings (no super low climbing gear) along with a 5-10lbs camelbak didn't help either.