It's a sure sign of spring.  Not that the robins are seen or the kids are outside.  But that they are getting ready for the budget on Beacon Hill.  Massachusetts legislators debate the state's $36.2 billion budget bill tomorrow. The improving economy and better-than-expected tax collections have some lawmakers and advocacy groups looking to increase funding for many programs. But the House budget adopts a cautious approach, proposing nearly $200 million less in spending than Gov. Deval Patrick.