Driving in the north of Spain at the end of April

I'd probably do a loop. Like a trombone, extend it or shorten it based on how much ground you like to cover. Shortest, Montserrat, Zaragosa, Pamplona, San Sebastian then work back to Girona. A little longer add, from Pamplona, go to Burgos, Bilbao, San Sebastian and back to Girona. Still longer, detour south from Burgos to include Valladolid, Salamanca or north to cover more of the coast west of Bilbao.

Thanks Brad. With so much to choose from it is nice to hear from people like you who are in the know. I'm quite curious if it is too early in the year,( end of April), to go as far north as Ripoll and Puigcerda, possibly crossing into France at that point. Or following the N260 across the north.

Not sure if you plan to stay somewhere else before Girona or are day-tripping out of Girona, but -
If you want to catch some Dali sights, a short distance to the east there's Pubol (Gala's house). Continuing east, Peratallada is a gorgeous small town ... beautiful! On the coast, there's the extensive Greek and Roman ruins at Empuries. And then a short distance up the coast from there is Cadaques and Port Lligat (Dali's home) - a great spot for an overnight.

Peratallada and Empuries are very good suggestions! We stayed in a small town called L'Escala nice little place with an outdoor market and some good restaurants.