If not, which would be best to plant?
I'm in Denver.
Plenty of time for direct sown stuff such as parsley, cilantro, thyme, corn, okra, cucumbers, beets, carrots, winter and summer squash. Too late for peppers and tomatoes unless purchasing plants to transplant. Also probably to late for peas, lettuce, spinach or other cool weather plants though they can be sown late July to mid August.
This a great little site to determine what to plant and when. To find your first and last frost dates you can go here:
Here is a link that might be useful: GrowGuide Seed Starting Planner
For herbs, you're fine on nearly all of them. Just know there's the fast growing annuals that are good to direct sow (basil, parsley, cilantro, etc). Plenty of time for those, in fact it's just now getting warm enough for the basils. Cilantro is a semi cool season plant--you'll get lots of leaves to start with, but it will bolt to seed pretty quickly here too as soon as it really heats up. Then, just collect the coriander seeds!
Then there's your perennials: rosemary, thyme, oregano, sage, lavender, etc. You can seed these in, but you won't get much of a harvest this first year on the slow growing perennials. Better off to buy transplants of them if you're not planning long-term. Most of the other herbs you're good on too, especially if you start with transplants: savory, sorrel, burnet, chives, etc.
Another note: if seeding, some herbs can have a long germination period (30+ days) for things like parsley, oregano, lavender. Rosemary, marjoram, lemon verbena and other tender perennials will not survive winter here in most cases.