Sounds like a heater core is leaking. That is a very common problem. You will be far better off to have both the heater core and the AC evap replaced at the same time. they are both in the dash and they both commonly go bad. fix both with the same labor.
water in passenger floorboard, where is the hose that would cause this?
A damaged heater core will cause coolant or water to leak onto the passenger floorboard.
passenger side floorboard on the firewall close to the kick panel
Does it smell like antifreeze? If so, it is most likely a bad heater core, or one of the hoses feeding it.
ac drain stoped up or heater core bad
It sounds like you may have a bad heater coil. Next time you get a puddle, smell it... Chances are it is coolant and not water
There is no drain plug but a condensation drain tube located on the passenger side firewall or just below ( rubber tube sticking out ) It may be plugged and a coat hanger or compressed air will open it. Your heater core may also be leaking if there is also coolant on the floorboard. If so it will need to be replaced.
There are many things that can cause vibrations in a 2000 Toyota Avalon. One such cause could be a bent rim and another cause for the vibrations underneath the floorboard is the engine.
heater core
Water.
If you left the vent open, or if the vent under the windshield is full of leaves, it could cause rainwater to flow into the floorboard.
Yes, yes it would. and if you pull down the inspection flap on the passenger floorboard under the glovebox you will the the righthand indicator light flashing a code 17, denoting the vss is faulty.