PHILADELPHIA - "Are we really doing this?" I asked myself as my guest and I navigated the subway, clumsily carrying a folded table and two chairs. I'll admit, I was a Dîner en Blanc skeptic. The effort—the all-white dress code, the secrecy, the self-catering—seemed like a lot of work for a dinner party. I had been assured it was worth it, and last night, I found out why.