I don't participate in any group rides. However, I do ride with my husband who is usually a couple miles ahead of me, so I might a well be alone! This year we are taking a new tact. In St. Louis, between Trailnet and Hi-USA there are organized rides pretty much every other weekend. We can start together, head out for different distances, there is a well-thought-out route (usually on a new side of town we haven't discovered), rest stops and support. Not to mention you may find a new training partner.
If you are training alone, I recommend checking local bike shop web pages for routes. Loops are best, so you can restock food and water at the car (or bail if the weather takes a turn). However, a well-planned route will include gas stations where you can fill up. Carry spare tubes and leave a "flight plan" with a friend. I used to need company, now I prefer the peace and quiet, with the wind in my face
"Well-behaved women seldom make history." --Laurel Thatcher Ulrich
'09 Trek WSD 2.1 with a Brooks B-68 saddle
'11 Trek WSD Madone 5.2 with Brooks B-17