I was travelling east on Lawrence Ave. just past Allen Rd. I made a right hand turn onto Shermount Ave. and there was a no right turn sign during the time I made the right turn. I was travelling to a house on that street for work purposes, so I assumed I was considered local traffic when making the right turn.

Unless there was some type of signage exempting local traffic, you're still not allowed to make the turn. As stupid as it sounds, with all the "no turn" signage along Lawrence, I think you'd have to head right up to Bathurst to make a right, then loop back around. I'm not sure if it's still common or not, but some people have had luck getting the charge plead down to a bylaw offence, which is less likely to impact your insurance rates.

Yes I would have had to travel down to Bathurst. When I go to court, should I ask to have it pled down to a bylaw offence?

Give it a try and see what happens. Can't hurt to ask.