2 hours 30 minutes via CA-62 and I-15 S (~140 miles).
No direct rail. Train from Palm Springs to Las Vegas, then bus/taxi to Twentynine Palms: 5–6 hours total.
Fly Palm Springs (PSP) to Las Vegas (LAS) – 1 hour flight. Then rent car/taxi to Twentynine Palms: 3–4 hours total.