Yes! In my first game jam I have never made a game with Unity and ended up making a game in 48h straight (with about 4h of sleep per day). If you manage well those 48h I think you can learn while making the game and end up with something quite nice! And even if you use the 48h and still didn't can't finish the game, try to finish it and instead of sending in the jam (because the rules etc) just send to friends and know game devs to give you feedback about it.
Hope you manage to give a entry in the jam and learn a lot and have fun doing so ^^