The hilly Hillcrest Open Space Preserve is covered yellow and purple in a display worthy of view. In fact, I’ve never seen this much lupine in one place in my 25+ years in the Conejo Valley. The Hillcrest Open Space main trailhead is not the easiest place to access due to the lack of any parking on Hillcrest Drive in that area, but there’s also another entry point highlighted in THIS POST. You will also enjoy the colors just driving by.
Not particularly the best trail for young kids as it is one of the hillier trails in the area. But not a problem for some. (On that note family and stroller-friendly local area trails at THIS LINK.