I think using a mounting block is OK - I do it sometimes. ;) I'm only 16, LOL! :P But anyway, if you have trouble mounting from the ground, I've found that taking your stirrups down a few holes helps. But then again, if nobody else is there to shorten them up again for you (or you could do it while you're in the saddle, but that can be difficult!), then maybe that's not a good choice.
I think using a mounting block is fine, though.
Success comes a [bit] at a time.