A f2.8 zoom is always more versatile for events.
There will be times you might not want to use flash or want more isolation thru DOF control.
That said, if you use flash, a lens like the 18-135 is pretty effective too considering that you can go real close with it even at 135mm.
For streets, which is mainly outdoors in good light, I'd give the advantage to 18-135 for the focal length options.