It does have its uses - to keep drainage material from washing out from behind a dry-stacked stone retaining wall, to keep soil in a basket where you want to plant annuals, or under a walkway to separate layers of soil and drainage material, but you will come to regret ever using it where there are plants growing in a garden.

Instead of using landscape fabric, I mow down everything to ground level and sometimes will dig a few weeds that I know to be stubborn, put down heavy cardboard and then a heavy layer of medium fine mulch on top of that to a depth that settles to about 3 inches. That's enough to prevent most weeds from sprouting and to keep most of the already present weedy plants from coming up through. I let that sit for a few weeks to a year and then plant. If you are in a hurry to plant, though I can't imagine that this is a great time to plant in most areas of Colorado right now, you can use some type of contact weed killer (they range from gas flame weed torches to strong vinegar to Roundup.)

One more quick comment - since you are planning to redo the whole area, now would be a perfect time to add any soil supplements like more organic matter to help hold moisture and nutrients.

Whether you are planning a new bed or rehabbing an old one the investment of time to do it right the first time is crucial. If you skip steps or do a half a**ed job you will be playing catchup and redoing things for the next ten years.

It's June already so too late for spring planting anyway.
Two choices:
Dig out all the plants.
Amend the soil.
Grab a chair, a cool drink, and study up on plants and and plan your design.
Plant in the fall.

Or if you really want a great bed:
Dig out all the plants.
Amend the soil.
Lay cardboard or layers of newspaper over the entire surface of the bed and weigh it down with compost.
Do your research and planning over the winter.
Plant and mulch in the spring.

But don't cheap out and try and do things the easy way.
You will be kicking yourself for years.