If you want to go gonzo, you can certainly shoot for the fully Israeli pronunciation of ר RESH. If you want to sound like beloved weatherman Robert Olinsky, on the other hand, you can hang on to your English r, and people will still love you. 

Former Prime Minister Ariel Sharon, who died in 2014, was a fluent English speaker who never quite lost his Hebrew-style "r," pronouncing it much more on the back of his soft palate like ר   RESH