Hello Paul. 😀

"Want to do the Blues and Rock course and not sure if I should do LVL1 with both before going to LVL2".

Mixed messages in your post, so not clear what level of personal playing competency you're at. But re your question above, If I were new to this curriculum I would if it was me and I hadn't covered the material before or wasn't sure if I had. If it turns out you already know what's covered in L1 so it's essentially revision for you, you'll breeze through it in no time, but leave no gaps in what's required to progress through L2. The approach I would take is pick one, either Blues or Rock and do L1 followed by L2 before progressing to the other. 

Welcome.