This depends on what you wanna do :) Mostly it is better to have a small team, due to separating tasks, like for example: You do the Coding, another one does the art and another one puts it all together in the game engine or so. It may be better to be in a Team, if you don't have any code/art/design experience. But sometimes its also cool to make it all on your own, by finding the Idea on your own, making the game as good as possible with all your skills you have and then in the end you can actually tell, what you have learned for these two days. But it depends on what you want to make during this jam :) If you find some nice people to work with, then it can be total fun to create a game from scratch, but it can also be fun to make it on your own. 

I think, for such a short minijam, which is only digital and only lasts for 2 days, I would say, try it on your own (besides you find enough people that quick before the jam starts), because I can imagine, that the Brainstomring Process can take a while, when being in a team. But thats my point of view! :P 
I hope I was able to help you a bit.