My suggestion, if you want to be prepared for any street encounter, is to be sure that you are familiar in all ranges of combat: weapon range, punch/kick range, trapping range, standing grappling, and groundfighting.
Sifu Francis Fong's Academy is an excellent choice.
I've studied Aikido since 1991 and while I love the art, it generally takes a long time to make it work comprehensively, due to the ritualized training method. Not to mention that 90% of the "Aikido" instructors around are New Age weirdos that have completely taken the martial aspect out of the art.
Ultimately, check out a bunch of systems and schools, and pick the one you like best and covers the most ranges. If you don't enjoy what you are training, then I think you are wasting your time.
Tim
http://www.streetpro.com
Street Smart Professional Equipment
http://www.streetpro.com/ewc2000
Edged Weapons Conference 2000