Re visiting Yosemite, it depends on time and budget.
In April, some of the roads will still be closed and some of the main routes may require snow chains to be used. Tours will still go ahead and some campsites will be open. But the half dome walk amongst others will be closed.
It takes a good 4 hours to drive from San Francisco, so most people go for at least one night. But you can do a day tour, with about 3 hours in Yosemite Valley (where the most photographed views are).
If you are trying to stick to a budget, note that campsites and other accommodation might already be booked up, particularly for weekends. The National Park run a reservation system where the April camping sites were released for booking last November/December. NP reservations.
I would say hiring and driving a car in the US is easy and can be cheap and gives you extra flexibility.