If a player can keep time I’m all for it. Being ready imo is all about timing, and not so much about playing at an intermediate level.

Being ready might mean a different thing for those making the music (?) and those listening to it.   

Either way no permanent harm is likely to come from it .... fwiw,  I say you're ready.

[I've been told a few times by reasonably accomplished musicians that my timing is "good."   As for making a worthwhile contribution to a jam ???  I guess .... IF 3,2,4,1/3,2,4,1/3,2,4,1/3,2,4,1/etc.  more-or-less in time can be considered worthwhile.... ??  ]

You’re a musician, so you’re ready. Some songs work better with clawhammer than others so I would just suggest pick your material wisely.

And more importantly Laurence, at one of the jams in our area we stop mid-way for a v-e-r-y good lunch.  The MC reminds everyone to let "the musicians" go first.   That in itself is reason enough for me to be a participant (?).   

I'm reading a lot of ‘me’ talk. A big focus on what you’re ready (or aren't ready) to 'do'. A session isn’t a competitive or individual performance space; it is an ensemble and musical support space. If you think a little more about the musicians you will be playing with you’ll probably survive. You might even get invited back.

… if you’re only a month in you’re still in ‘conscious concentration’ mode to coordinate your hands and maintain accuracy. Too early? In my view, before technique is second nature, yes it is too early.

But if you're set on going then Simplify. Simplify. Simplify. Because a month in, your brain will be fully engaged just trying to do the basic r/h stroke and attain some level of accuracy. In that scenario your brain has no spare capacity to deal with all that a session demands of you.

The issue with going to a session too soon is that it can evaporate a player’s confidence. That can really set a player back; I’ve seen that happen many times. It doesn’t have to be that way if you prepare and acquire a few coping strategies first. Coping means ‘joining’ and joining is when you can start to pick up the skills you need.

"You’re a musician, so you’re ready."

Why I have never heard such a thing in my life! All these years I have tried so hard not to get arrested for impersonating a musician. I am going to re-examine my illusions and delusions about all things banjo.....banjered

IMHO, going to jams, sitting in the outer circle, listening and watching, and playing along (quietly, at first) is the very best way to get comfortable with a jam environment. Pick the strongest fiddler and watch their bow hand, helps focus in what can be an acoustically challenging situation.

Have fun.