The reason sunlight should be avoided is because UV light damages skin cells, including hair cells, as well as it slows down proper healing of grafts. It should be avoided as long as possible until the grafts have grown. Six months is a fairly liberal suggestion because we all know that it takes somewhere between 12 â€“ 18 months, sometimes even longer, for the grafts to heal properly and all the hair to grow.
A tanning saloon is hybrid UV light, which is much, much worst than direct sunlight. If I had to choose, I'd rather be on direct sunlight instead in a tanning booth.
But than again, some people are much more resilient against sun light and are able to be exposed to it without complications. Genetics play a major role. If you'd ask me, I'd avoid UV light as much as possible even though it is very hard to do during the summer season. At least wear a hat or something to cover your head.