Can I leave speaker jumpers in?

Do not leave the jumpers in when bi wiring.  It will sound funny.  But it won’t kill anything. 

No remove the jumpers when using the Bi wire cable or put both end of the bi wire cable to on speaker imputes then use the jumpers from there to the other impute. Make sure amp is off when switching wires,

It's been my experience that if you have a speaker that has two sets of terminals the jumpers that come with them are usually made of some type of inferior stamped metal.
Almost any copper wire that you put between the posts would be an improvement over stamped metal jumpers.
Even a good pair of 16 gauge copper wire pieces per side, would do the trick.And it's an improvement you can easily hear. Especially in the upper mid-range and treble. It's one of the cheapest and most effective tweaks that I've ever used.

I wouldnt leave jumpers in as no benefit to biwire cable. It should only take seconds to put jumper in. But do a listening test as if you can't hear difference then don't bother 

I’m trying the jumpers in, even while using BiWire cables.  Initially a little more laid back presentation.  Using MIT Magnum jumpers with MIT REV 60 cables.  Fun experiment!