If you use the savings bonds to pay for college, you won't have to pay taxes on the interest earned. To do that, you have to cash them in the same year you use the funds to pay for college. So you can just put them aside, and wait. more info here:
http://www.treasurydirect.gov/indiv/planning/plan_education.htm
If you think you can earn a better return somewhere else, you can cash them in now, and put the funds into the 529 or wherever else you will get the better returns.
You can check on-line to see what the bonds are earning:
http://www.treasurydirect.gov/BC/SBCPrice