@JoeP:  Well, I don't have a few years on violin yet.. But I have some years on other instruments and have done some of the things on your list, so I'll chime in and maybe you'll find some of it relevant.

1.) Community Orchestra/Ensemble.  -  Haven't done that.  

2.) Play solo for friends and family where it's actually fun for all involved -  As soon as you have the cojones and the sense of humor to give it a shot.  That could be day #1, if you're wild and crazy enough.

3.) Play solo at a local park or coffee shop - With the park, what's stopping you?  I went down to the park to play a few times in my first year with violin.  That was probably at 3 or 4 months.  Sometimes people would stop to listen for a while.  Try it, it's cool.   A coffeehouse, well if they have an open mic that doesn't require an audition, you could do it starting whenever you want.  If it does have an audition, then go and see if you can pass it, if you want to play there.  

4.) Play solo at a local small casual outdoor concert -I've done those in years gone by, both in bands and solo.  Also helped organize some of those events.  As one of the people who had a say in who got to play, I can tell you that some of the people who played had been at it for less than a year, but they had a couple songs or maybe a few songs down well enough to give it a shot. 

I got asked to do something somewhat similar (but not solo) for a local community event last year where they hoped I'd show up with violin (or anything else I play would have been ok as well).  Maybe a little different than what you mean, though.  For this event you just got a sheet of music and show up and play, no rehearsals or etc.  Fairly large number of area musicians participating, some coverage by local media.  That was at about 6 months on violin, so I'd say it is possible any time after 6 months for sure.

I didn't do that event, but it was because of family obligations and short notice, not because I wasn't "good enough" for that sort of gig. 

5.) Play rock and blues, well - LOL  Problem is, you'd have to define "well".  Are we talking you get applause, you get paid, or what?   It depends on other factors too.  What kind of other musicians you're playing with the repertoire, the crowd.

A lot of the things you listed, though, Joe.. They aren't about being "good enough", or at least that isn't entirely it.  You can play so good it would make the ghost of Jascha Heifetz himself weep.. But if you don't network with other musicians, take a chance and play in front of other folks, audition for a gig you want (even if *you* don't think you'd get it), then you can still end up never playing for a bigger audience than the 4 walls in some room of your house.  For at least some of the things you listed, it is more about finding or creating the opportunity or just plain going ahead and trying it than it is about being "good enough". 

But having gone back and listened to your take of Londonderry Air in November, even right then you could have just gone and done some of the stuff on your list.  It isn't a lack of being "good enough" that is holding you back from those things.  That is true of quite a few people here, though.  Playing for friends and family, playing in a park, trying a coffeehouse.. Why haven't you?

All I'm saying is that other then the last item, which only specifies being able to play blues or rock *well*, all the rest of it falls under stuff where just getting "good enough" won't get you there.  Networking, doing a little promotion, maybe hitting a few auditions, and with some of it, just getting out there and doing it are what you're probably lacking so far.  If nobody knows you're there, then it may not matter how good you ever get.  

Now, if you mean doing all those things and actually going over well with the audience?  Well, there's never a guarantee on that for anyone.  But you try it and you see.  How listeners/audience react to your music is some of the feedback you need to get good, I think.  Finding out what goes over and what doesn't is part of how you fine-tune your sound and your selections.

@Composer:

"Certainly, any credible orchestra should expect someone to be able to do that."

  LOL  So you don't actually know either?   Well, at least you admit it.   Didn't expect you did, actually, since i don't recall you ever mentioning being involved in orchestras as either administration (who would actually decide such things) or as one of the players (who have to live with such decisions).