Worthy Bulbasaur level to evolve?

I am level 24 now and I got one with a higher CP than yours, if you are near parks, it is easy to obtain another one.

I wouldn't recommend it, unless you have an excessive amount of candies (250+). Venasaur is a pretty good pokemon right now in the meta, its better to wait.

I'd say go for it. I mean, you could find technically a better candidate, but then that candidate could get evolved and have a meh moveset anyway. At least if you do it now you're getting the XP for a new index entry (twice if you don't have ivysaur, doubled if you evolve with a lucky egg) while it's still worth something to you (after level 30, leveling is just grinding and pain). And if it works out, you have a good attacker with a decent CP (541 is in the level 20 range, right?).

I'm level 30 now with decent access to Bulbasaurs, but from my own experience, egg hatched ones (so level 20's) are the best IV's out there. I've had a few 600 and 700 CP pass my way, all tough as hell to catch and all under 70% CP. Might just be me, but I'd take the chance on getting a good Vape-killer now.

I had a similar issue with Squirtle - a few hatched lv20s and whilst I caught a few wild ones with higher cps none had decent IVs. I evolved one of the lv20s and of course then found a wild lv25 with decent IVs three days later. I was slightly irritated but having said that a month on and that one decent wild Squirtle hasn't been matched or equalled.

In short there's a chance of getting a better one in the wild but you could be waiting a long time. Most caught Pokes will be lower.