Agree with answer above - delta is roughly 0 ATMF. But it is model dependant.
As the 2y10y fwd moves, your straddle will accrue delta (new delta = old delta + gamma * curve move). so as you accrue delta, you may decide to delta hedge. Note if you are long the straddle, as the market sells off, you get shorter delta, as the market rallies you get longer.
For eg. if the market sells off 20bps, you are now shorter say 20k Dv01 => you need to receive fixed (to flatten your risk). Now if the market rallies back 20bps you go to flat again => you need to pay the 20k you just received. You've net made money by just flattening your risk. This is gamma trading - for this grand privilege, you pay your daily carry. So if the market doesn't move at all, you just lose your theta. Therefore, gamma trading is all about weighing out implied vol (the cost of theta) versus realised vol (the actual volatility which the underlying endures during the life of the trade).
The move to outweigh the premium spent: the 10y fixing needs to reach (strike) +/- premium spent/Dv01, at expiry of the trade for the straddle, for it to breakeven. i.e. it needs to end up more ITM on any side than what you paid for the options.