Question about a phone wall adapter and it's current output
Current is dependant on voltage.
If you have a small load it will draw a lot of current, if you have a large load it will draw small current. 
The 5V @ 2A indicates that it's rated to handle up to 2A at 5V. 
The other day I took an old phone wall charger (similar idea), made sure that the RGB LED's didn't go over their rated voltage and plugged it in!
If you think 5V is too much you can always add a resistor in series with your LED's.
Hope that helps!
Josh