Yes, you can use most keyboards just fine. Some adapters are needed though.
If you want to use "newer" Amiga keyboards, like the one coming with A4000, I think you would manage with AT-PS/2 adapter. (If you would want to use black Commodore CDTV keyboard, you would need to modify the keyboards connector a bit, as the pins are in different order.)
For PC keyboards, there are few adapters for them as well. I'm using adapter called Lyra. If I remember correctly, there are similar products available from Amiga resellers. You will probably need to use that AT-PS/2 with them as well, since the connector is the bigger AT style in your A2000.
