I visited Phanom Rung in March this year. Definitely worth seeing… It was great.
I like small motorcycles, so in Buriram I rented one for a few days, and one day I rode out to Phanom Rung.
It was an easy ride, good roads, not much traffic. Took less than an hour to ride their, and I even found a nice little Thai restaurant on the side of the highway to eat at.
If you are comfortable riding a scooter, I recommend that.