Hey @Newbie3312,
Thanks for the tag @Sister .
I run a horse boarding and training stables. I was back in the saddle about 4-6 weeks after (mind you riding after chemo throws your balance out it interesting). I just chose the horses I worked with for a while so I didn't get that arm pulled on. It made dismounting a bit difficult for a while (short girls always ride tall horses huh?) I just made sure I let go and jumped off with that arm clear. Watch that one it hurt.
Anyhoo, if you've got a good reliable horse to start on for a few weeks you should be fine soon enough. I cannot stress how important those exercises are though. Do what they give you then double it. Everything you can do above your head will help. I chose to hand paint a tongue and groove ceiling as my therapy.
Don't worry sweet you'll be lugging hay bales and shovelling poop before you know it.
xoxoxoxoxo