I have two language packs on my Invision Community - Spanish (PR) and English (USA).

Is there a way that I can make a URL to open the site on one language or the other?
Eg. mysite.com/?lang=es or something like that.
I noticed that each language has an id so I'm hoping there is a way to do this.

There is no way in which you would be able to do that at the present time. You would require customisation in which to achieve something like this.