A topic I see come up often is that of exploring with partners or groups. Is it better to explore in groups, or alone?
The first point to consider is that, in my opinion, it's a bad idea to explore anywhere alone. There is always a chance of something unexpected happening and you may require someone else's help. You can bring a cell phone along, of course, but there's nothing to say you'll be in a condition to use it.
The second factor to consider in this is the location to be explored. Is this a place where there is a significant chance of being asked to leave, caught by security or charged by police? If so, I don't believe groups are a good way to go. On the other hand, if the location is fairly remote with little risk, groups can actually be a lot of fun.
A short time ago, I had a situation where the noise being made by other explorers (not with me) was creating a serious risk of drawing unwanted attention. This is something you can do without.
The third thing to consider, regardless of the size of your group, whether 2 or 20, is how well you know them. Do they compliment your "exploring style"? If something happens that requires quick thought and smart action, will they react as you'd expect? Can you trust them to be quiet, respectful of the property, to have the same values you do? If you move quickly, will they hold you up, taking all day to capture that perfect spider web? If you prefer to take your time, will they be badgering you to go faster?
The more people you involve in anything, the more complicated it becomes. It's harder to plan dates and times that everyone can make it. It's harder to agree on how things will be done. It's harder to fulfill everyone's styles and expectations in a way that everyone will get what they want from the experience.
In other situations, perhaps depending on the neighborhood, etc., there can be safety in numbers.
All in all, this is a very personal choice, and one you should consider carefully before either forming your own group, or joining another. Even selecting your one partner to explore with can take time and experimentation.