Nice to see a lot of people interested in cycling trips to Nandi.
I don't want to demotivate you but Nandi is a huge crowd during weekends. You need to be extra cautious as I have seen some silly Bangalore youth who have their GF's (or whoever you know!) on pillion who come carelessly close to you as and start teasing you just for their adrenaline rush that a girl is sitting behind and start acting weirdly as if they are playing a game of road rash or something!
[The reason I say this is coz during my recent ride back home one-sick-physco on his apache came close to me and started pedalling in air next to me just to tease me! I was about to kick him but he escaped and sped away but later I see that he was caught on police speed gun :) I felt quite pleased as I overtook him and showed-him-middle-finger while he was begging literally at the feet of the inspector]
They don't value the cyclists. According to my experience couple of times now, the place isn't safe too. People get mugged if they are isolated. So try to ride together.
Carry tools with a patch kit! Long time back when I was a first timer to Nandi on my Hercules MTB, The mudguard broke! and fell off skidding past the tyres and got stuck. I had to manage to cut it off with a hacksaw as I had no tools! One of the good learning experiences is to fail :)
You can take the SH74 Dobbaballapur route till the banyan tree (ask for locals) and then take left turn or take Right turn from NH4 further about 22 kms. (I feel NH4 route is wider and safer from incoming traffic)
You get bananas and tender coconut at a lot of places enroute. Also there is an idli point also at the base of Nandi for some decent lunch.
Since you say many are first timers, you may get really tired on the way back. You can stop after the flyover junction soon after airport checkpoints to take a volvo back to bangalore. Some drivers are considerate to carry if the bus is fairly empty.
Cheers!
Happy riding,
Karthik