Had to chime in with my two cents here. If you have quail / chickens, you can raise chicken / quail. Having one does not exclude raising the other. Crank over the ol' incubator or put in an order to your favorite hatchery and get some of both.
Now, that being said, I do know a few things either by way of reading several thousand of the posts here, reading several thousand websites, or through trial and error.
1. To a chicken, quail look and taste like grasshoppers. Unless you have developed that magical elusive quail called the 10 pound bob, chickens will hunt down your quail and beat 'em up.
2. Unless you plan on flight-training your quail, keep them in squatty pens 2.5 to 3 ft off the ground or clip their wings. Quail, from buttons to Butler Bobs like to "popcorn" when startled. As a result head injury and death can occur, especially when big food monster appears suddenly overhead. Also, 2.5 to 3ft off the ground helps when you have a lot of quail to feed and water and a sore back.
3. Domestic quail are a bit hardier than wild varieties when it comes to illness but they are still more susceptible to some diseases than chickens. According to a friend of mine in the Texas A&M poultry science department (the same section that developed the white A&M cotunix), all breeds of quail are susceptible to chicken diseases. However, those quail that have been developed as hybrids or have been in the captive state for some time (minimum of four generations) are not as quick to catch chicken diseases as their wild cousins.
4. Quail and chicken chicks can be brooded together for up to the first 3 weeks. Same fella also says that one should feed BOTH quail and chicken chicks medicated food during this time and actually endorses this method of brooding for those who raise both types of birds because it exposes the quail to those diseases present in the chicken population allowing the quail to start developing antibodies at an early age before any form of medication resistance can be formed. When asked why medicated, he shrugged and said that it couldn't hurt. However, the SECOND you see the chickens looking at the quail with a "Hmmm, is that a grasshopper?" expression, separate.
5. Quail and chicken can be housed within a 10ft range of each other IF some precautions are used. The quail pen needs to be placed so that any prevailing wind hits it first then the chickens. This way airborne diseases are less likely to carry into the quail cage. If the quail are in a raised pen, they can be side by side to the extent that the quail can literally look down at foraging chickens. However, if the chickens are placed in an enclosed coop overnight, then care must be taken to insure there is adequate flow of air away from the quail's nighttime sleeping area.
I translate all this into raise chicken and quail but use some common sense. If your quail begin to get sick, perhaps relocating their pen away from the chickens may be in order. Not only for the sake of the quail but the quail may have picked up something they can give to the chickens.