As for getting lost, I don't think you'd have a problem. It's a fairly major trail. The section from Oakwilde to Switzers is the least used, but even it is pretty followable. I've not heard of people getting off track. This section from Oakwild to Switzers is probably the most exposed, so you might want to do that one in the morning if the day will be warm.
John Robinson's book, Trails of The Angeles, is a good guide for this area. Robinson has also written Trails of the San Bernardinos which covers the San Bernardinos, San Jacintos, and Santa Rosas. I commend both of these to you. The map links are to scans of the maps from Robinson's book.
Parking at Chantry Flat, the east end of the loop, is pretty good. The gates are open only 6:00 AM - 10:00 PM. You must have a USFS Adventure Pass (that's a fancy name for parking permit). No problem with overnight parking.
Parking at the west end is OK, but not quite as good. There's a free, public lot on the NW corner of Windsor and Ventura.
http://maps.google.com/maps?f=q&hl=en&geocode=&q=Windsor+Ave+%26+Ventura+St+Altadena,+CA It's not a bad neighborhood, and I've not heard of break ins, but it's not secured in any way. You could call the Altadena Sheriff's Station and see what the regs are for that lot. You could park on a side street, but again check the regs. I've only overnight parked at Chantry Flats.
I went out today for a hike in similar terrain and at similar altitude. IT WAS GREAT. Late Mar through April is often one of the best times of the year for hiking in the front range of the San Gabriels. Of course, the weather has a mind of its own. You could get a hot or cold weekend, that all depends on the Big Guy upstairs. We had a cool weekend last weekend. Tomorrow will be hot. We're supposed to get a cooling trend into next weekend but on average, weather should be good.
Water should be pretty available this early in the season. If you look at the map links that I gave you the right side up, open triangles are overnight spots. Going clockwise, not that you necessarily have to hike that direction, the camps are: Oakwilde, Commodore Switzer, Valley Forge, West Fork, Devore, and Spruce Grove. All of these camps will have good water this time of year. Take a close look at the map. You're following streams much of the time. Any time you're following a stream on this route, you should have water this time of year.
Overall, I'd say this is a good time of year to hike and that you should have some nice hiking.
HJ