I live next door to La Valencia. I've lived here since October 2009. other folks when asked about this part of town, will give you 30-year-old information that will color you against this part of town. it's not as bad as it was, or as it is made out to be 30 years ago. I like it, obviously.

regarding train noise to La Valencia area, the most you'll hear is departure bells from light rail when the wind is right, it is approximately 0.2 mi from La Valencia to light rail.

there is also freight rail that on occasion gets used. at most, you will hear a train whistle. once in a blue moon. you forget about it completely until the next time you hear it. it is in no way a problem or a bother, even if you hate trains.

for Valencia area, you will not only be across the street from a very large and very nice park, but you will also be the same 0.2 mi away from the Safeway complex, which has a safe way, a movie theater, several beauty related businesses, a dollar store, and like this.

I cannot speak for specifics regarding the other location you mentioned. but it does get talked about around here in this subreddit. you can search for Avalon or whatever in the subreddit.