It would be pretty safe, and dividends would be better than just interest when considering taxes...
Bonds pay interest though so they are no more tax efficient that the savings accounts.
Also, bond prices can/will fluctuate, so I'll have to reiterate keeping the money as cash. You really have to ask yourself how important your timeline for buying your house is. In anything other than cash, you risk delaying your purchase by a year or more if there happens to be a dip in price at the exact time you want to buy a house.
Also, the upside benefit (maybe 2% interest) over a year or two is minimal. Say you have $15000 now, in two years, 2% extra interest in $300/year. Is earning an extra $600 worth the chance of NOT being able to buy a home if the fund value decreases?