I'm 5'6" and my lad is 15.3hh. Also sometimes ride sisters gelding who is 14.1hh and very occasionally sec c who is 13hh-ish (although I feel completely huge on her!)
I'm 5'2" ish and gelding is 15.1. OH is 5'10" and mare is 14.2.
I could get on from the ground but it wouldn't be pretty or comforable for either me or the horse!
I'm 5"5 and horse is 15hh - I have to get on from the ground as he's convinced any form of step, mounting block, boulder, slight bump in the ground etc etc is a monster!
The last horse I rode was 17.2 and no, I couldn't get on him from the ground and luckily never had to try!!