I usually wait until Mother's Day for tomatoes and peppers. Have pushed the envelope and planted May 1, but that can be iffy. Your zone 6 is probably not the same as my zone 6 since you're in the mountains. Suggest you ask at the garden center what your last frost date is. I do think you can do broccoli now though, since it prefers cooler temps.

It's hard to give an actual date. You need to wait until your night time temperatures are consistently in the 50's. Any sooner and your stuff will be stunted.

Snow peas, broccolli and beans should be ok now, But wait with the rest until at least 50 at night and 70 plus during the day.