I am a 5th year PhD ABD in Philosophy and my partner is a lawyer who also loves/studied philosophy as an undergrad...so I feel as though I may have a few experiences to share.
First of all, philosophy grad school is intense. So is law school. Be sure you love both if you plan on doing a joint degree. If you love legal philosophy for the sake of law, consider simply doing a JD--most good law programs offer excellent courses in the philosophy of law, philosophical ethics and legal theory. Additionally, many universities will let you take a few course in other departments--so you could take a course from the Philosophy grad department.
If you love legal philosophy for the sake of interest in socio-political philosophy, then consider doing an MA first at an institution that has faculty in socio-political philosophy, and then do a PhD in philosophy or a philosophically rigorous political science program. Signing on to do a joint degree unless you are absolutely certain it is what you want to do sounds like unnecessary torture--which as a philosopher of law, you should be able to analyze :wink:
Being a good student--which it clearly sounds like you are--is really only a minor part of true success in graduate school. It will definitely improve your chances of getting into a program, but once there, the passion for your discipline and dedication to your research counts for much more. Make sure you have that passion for whatever it is you decide to do, and then you will clearly know you are ready.
