I wouldn't be as discouraging about the weather prospects as some have been. Sure the high passes will still be snowbound in early May, but one can plan a trip to avoid those and still see the lower areas of the parks.
Our club has an annual ride to Yosemite from the SF area in mid April (leaving on the 19th this year) and the roads have always been open (Hwy. 120 over Crane Flat on the way in, and down the Merced when leaving). We've sometimes encountered snow showers but usually the weather has been pleasant. Keep an eye on the weather forecasts and be prepared to alter the trip routing if necessary - but it probably won't be. Early spring is an excellent time to see the park's rivers and waterfalls.