Iguanas should be dealt with humanely. Startling people and eating plants surely shouldn’t be cause for a death sentence.
In general, iguanas want to stay away from you as much as you want to stay away from them. Make your property unappealing to iguanas. There are many plants and ornamentals that iguanas do not eat, including citrus. If you have non-citrus fruit trees, don’t let dropped fruit stay on the ground. Seal access points like spaces around doors, windows, and plumbing. Make sure your screens are secure and undamaged. Keep brushy areas where iguanas like to nest to a minimum. Hang cheap CDs as wind chimes from trees or prized plants (the reflective surfaces can scare iguanas away). Nonlethal deterrent sprays are available at hardware stores.
Living in harmony with free-roaming iguanas is possible without having to bash their skulls in.