I need to change my sand after this season. Wondering if its better to do it when I close this fall and leave no sand in the filter or should i leave it and do it in the spring?

Thanks

I don't know that leaving it empty would hurt anything, but it sure would be nice to have it ready when you open up in spring.

Why? Are you having trouble filtering? Not much evidence for sand "wearing out". See this post: http://www.troublefreepool.com/sand-filter-expert-help-t30049.html#p247326

As long as you drain the water, it shouldn't matter. It won't hurt the filter either way, unless you move it carelessly with the sand in, or wind blows the empty filter around during winter.