Of course you can use those rates.
But I would not trust ADC at that speed.
2Mbit for serial is possible, but I am not sure your AVR can handle it if using interrupts. If FTDI chip rx fifo was a bit larger, then I guess you could use it.
selfonlypath did a lot of testing at higher baud rates, he found the error rate too high. I'm using 3Mbit on ZPUino with not many errors (with a FTDI chip also), but I have an hardware 2kbyte fifo. Helps a lot.