Between 4-5 hours depending on the route.
The quickest route is to take I-5 to Hwy 38 (toward Drain, OR) over to Hwy 101 at Reedsport, OR and down to Bandon. (4:15 hrs)
You can also take I-5 to Eugene, OR and then go out Hwy 126 to Florence and then take Hwy 101 South to Bandon. (4:45 hrs)
The final option is to take I-5 down to the Roseburg/Winston, OR area and then take Hwy 42 West to Coquille and then Hwy 42 South to Bandon. (5:15 hrs)
Around 9 hours depending on the route.
The most common route is traveling by I-5 to Hwy 42 at Roseburg/Winston, OR and over to Coquille and then to Bandon via Hwy 42 South.
Another route is cutting over from I-5 at Grants Pass, OR through Cave Junction to Hwy 101 just north of Crecent City, CA.
The most scenic (but lengthy) route is to take I-80 West to Hwy 37 in Vallejo to Hwy 101 at Novato and then up the coast. This is the most common route from San Francisco.