Needing to take a load of stuff to the dump, I attempted to confirm days/hours on the net. I couldn't find anything so maybe this will help you.
First, while the dump, actually a transfer station appears to be operated by Waste Management, signs say Palomar Transfter station and the operator is an "Allied Waste Company"
The facility is open to the public 7:30 AM - 4 PM Saturday and Sunday. It is closed on Thanksgiving, Christmas, and New Years.
The commercial hours are Monday-Friday 8-5 and Saturday 5:30-4.
The posted phone is 760-603-0153.
Palomar Transfer Station
5960 El Camino
Carlsbad, CA 92018.
Check out related services for recycling at the same site.
Map
You actually find the place on Orion between Faraday and Palomar Airport Road.
I paid $9.45 for a load consisting of an old chair and two twin mattresses as well as two bike tires I was surprised they would accept. Car tires are not accepted.
A sign says to make out checks to "Sycamore Landfill"
A rate increase was posted for June 1, 2008