John Donovan There are a handful of references to Dandelion Wine in Farewell Summer, but nothing that would make the sequel confusing. DW is a much richer book, so heck, I see nothing wrong with reading FS first--as long as you eventually read Dandelion Wine too!
Elanna You can read them as stand-alones, but actually, Dandelion Wine is the first part of a complex narration that ends with Farewell Summer. There are 55 years between the two publications, so the second novel has been polished and modified for decades. Bradbury explains it all in the afterword to the second novel.