Alabama Hills is basically in the shadow of the Sierra Mountains and that proximity can generate some pretty unpredictable weather. I camped there at the end of April and experienced high winds, snow flurries, heavy overcast, moderate rain, sunny skies with no wind, and a thunderstorm with several nearby lightning strikes all in the span of three days. On average the weather should be nice at that time of year, but check weather forecasts and be prepared for cold or rainy conditions.
Death Valley receives little rain and the rain is infrequent. Flower seeds can lay dormant for years until a large rain event and then the area explodes with growth over a short period of time. Owens Valley receives three times the amount of rain with the bulk of that arriving in the winter and early spring which leads to a wildflower bloom that's less intense and spread out over a longer period of time.