Something is eating my holly hocks. I am not sure what it is. What would be good to spray them with?

Japanese beetles love hollyhocks. Get rid of the grubs in your soil.

Just a question. Once my hollyhocks get to be 4 feet tall in the stalks, will cutting them back bring more blooms, or do we just let them run their course?

This person from another site sounds like they really know what they're talking about:

On Aug 14, 2001, gardendragon wrote:
Pruning: Biennial hollyhocks act perennial in nature if they are deadheaded and then cut down to new basal foliage as soon as all flowering is completed. Flowers from the bottom of the spike open first. Deadhead plants to lateral buds when seed capsules (on the bottom half) outnumber the new flowers (on the tip). Plants frequently seed if not deadheaded, leave the seedheads if that is the desired way to perpetuate the plant in the garden. Deadleafing is needed to remove yellowing leaves, starting in June and leaves damaged by Japanese beetles or rust.
Destory rust infested leaves. Cut out all old flowering stems and old basal leaves to expose clean basal foliage in late summer when flowereing is completed. The plants look so horrendous by this time that such pruning can be a welcome relief. The new foliage holds up well into the winter and may remain semi evergreen under consistent snow cover or in mild winters. Remove any winter damaged leaves in the spring. Tall growing forms can be cut down once or twice before flowereing to create later blooming, shorter plants that don't require staking, flower spike will be smaller but more in scale with the shorter plants and more useful for smaller flower arrangements.

Also, the reason I am interested is that we added hollyhocks to our garden this year and since it was my husband's project, I didn't pay them much attention until the leaves started yellowing and dropping.

The culprit: green stink bugs and lots of them. They were perfectly camouflaged. They wedged themselves up next to and between the bud clusters and were the exact same color as the plant!

If you have this problem, HG's Texas Bug Book says to handpick the bugs and crush the eggs; use citrus oil sprays for heavy infestations.