http://www.nicesemimarathon.com/v13/dl/SN2013-PLAN-SEMI-10km.pdf is the route map.
I theeenk its mostly flat - the prom is but there is that stretch out by the harbour that I think goes up a hill ? And then back round.
I know the Ironman marathon is flat and hot - but thats all along the prom and in August. I'd expect April to be much more pleasant.