Woodlice are dependent on moisture to survive, not surprising that in spring their numbers are great. As Aunt Sally said, they're good for chewing up dead plant matter and such into smaller bits.
If you feel you've got too many of these otherwise helpful creatures, then make sure 'problem' areas become drier, eg put away unneeded items, lift pot bases off the ground, floors, etc with props, hang hoses rather than leave them on the ground, clear up dead and flopping vegetation, etc. If they can't find damp, dark places to live, then they move on.