You can use your UK license for 6 months (7 years ago, that might have changed now). You will need to take a pointless 8 hr safe driving class where they show you videos. You will take an easy classroom test and the driving test here is a joke compared to the UK. It's easy just a hassle.

If the J-1 counts as a student visa and you maintain a residency outside the US then you can use your valid UK license while you're here.

You could ask at the DMV. As much as people complain about them I've found most of their staff to be fairly knowledgeable.