I know Cali has a crazy speed limit for trucks and trailers at 55. When the rest of the crowd is buzzing by you at 70+, it can seem intimidating. Do what your conscience tells you to.
However, since you're new to trailers, there is usually another limiting factor built in. Your tires are most likely only rated for 65mph maximum. When you have a chance, look at the tires. Unless they are marked with a speed rating, you need to stick to 65mph max. If you drive faster, the tires will self destruct and your trailer will turn into a mushroom cloud. Seriously, the tires are only rated for 65, and continually driving faster than that will likely shorten the life of the tire, and could result in premature failure.
Some tire manufacturers are starting to rate their tires for higher speeds. In the picture below, you can see the speed rating on one of my tires. It has a speed rating of "L" which is 75mph. This is not the norm for most new travel trailer tires.

Even though I have a speed rating of 75mph on my tires, I typically drive 63-65mph to save fuel, even when the speed limit is higher in states other than California.