As mentioned, there's nothing between Green River and Hidden Valley. It's up to you to traverse Corona/Norco in whatever manner pleases you. I've gone to taking 6th Street straight through the heart of Corona, all the way to Van Buren, then that to the trail, skipping the section between Hidden Valley/Arlington and Van Buren, because it also means I don't have to go through Norco. I don't believe the roadways in Norco were ever planned-- they just showed up, and no one has maintained them since. If you do decide to go through Norco, be sure to watch out for broken beer bottles and loose chickens, which you are likely to encounter in equal numbers.
When you get to Van Buren, you have to take the detour up Jurupa to enter the trail at Martha McLean/ Anza Narrows anyway-- they tore out a chunk of the trail back in April, and were supposed to have it replaced by August. Well, toward the end of summer they slapped a new sticker on the closure sign saying that it would reopen October 31st. That came and went, and the pavement is still missing. From Anza Narrows, it's a scant 3 miles or so to Bonaminio Park/ Mt. Robidoux, then about 10 miles to the current northern terminus at Waterman Avenue. In between, there's pretty much nothing. County line goes nowhere close, Mt. Vernon and La Cadena dump you out on the wrong side of the tracks. The closest thing to the La Cadena entrance is a strip club. No liquor stores, unless you're a local and know where you are and where to go. You could get a water fill up at Anza Narrows or Bonaminio, but be fully aware that the water is horrible. That is legitimately last-ditch water. You drink it only if you absolutely have to. At the Waterman end, you could hit a gas station about a quarter mile from trail's end, or head through the industrial park to some semblance of civilization. Costco's got an outdoor food court.
As to the trail itself, I love the top 10 miles between Waterman an Bonaminio. I'm out there at least once a week, about 8.5 miles from my house to the trailhead. It's clean, well-maintained, sparsely populated, and aside from the mile to either side of the Dog Park, generally devoid of people on foot. You can go as fast as you'd like. But it doesn't go anywhere. When the detoured portion is finally fixed, it's 18 miles between a street and another street. There's really nothing at either end. Now if you're using it as a highway to get into the IE and ride something actually scenic/worthwhile, sure. Not a terrible idea. Just be aware that once you get about 3 miles north of the trailhead the valley really starts to taper-- so it starts going uphill, and it never stops. If you like hills, we've got those in (almost) every direction.
Probably impacts no one other than myself, but the trail from Waterman to Anza Narrows is closed November 13-16 for maintenance. And when they say it, they mean it. Last time it was closed for a week, they cut huge chunks out of the pavement, then refilled those cut out chunks with poorly compacted asphalt, effectively making it worse in many places. Shout out to those guys.
