To save your legs by not climbing up Tai Shan, you can take simply take a bus up to the halfway point where cable cars will whisk you the rest of the way to the summit. I took the cable car back down as I had climbed up the second half of the mountain and then walked down the first half. Mind you, it's not cheap - RMB140 for a return trip or RMB80 for a single trip but the views make up for the expense.
If you don't fancy the hard climb up Tai Shan, you can simply take a bus up to the halfway point where cable cars will whisk you the rest of the way to the summit. I decided not to climb the whole mountain but instead took a bus to the halfway point and then walked up to the summit from there. The bus costs RMB20 to go up and RMB18 to go down. They leave from the large roundabout area by the main entrance.
Bus 3 from opposite Taishan train station goes to the base of the central route (Hong Men) and also stops at Dai Temple before that. Bus 3 from in front of Taishan train station goes to the base of the western route (Tian Wai Cun).
Bus Tai'an -- Jinan could arrive at any of the 6 (?) long-distance bus stations in Jinan so make sure you know which one you're going to. There seems to be more than 1 long-distance bus station in Tai'an, a little confusing. Ours cost 17 RMB, arrived in 1.5 hours at the long-distance bus station opposite Jinan train station, very convenient. There's a KFC right beside this Jinan bus station with clean squat toilets in the basement, very convenient.
Cable car in either direction for Zhong Tian Men (Midway Gate of Heaven)/Peach Blossom Park to Dai peak (note that these are 2 separate cable car routes) costs 45 RMB one-way, no discount for round-trip.
Cable car in either direction for the "back route" to Dai peak costs 20 RMB one-way, no discount for round-trip. We passed by this one on the way up and it wasn't even running, not surprising considering how few people there were around on this route!
Bus "you" 2 (Chinese character meaning "tourist"/"travel") opposite Taishan train station terminates at the starting point for the "back route" via Tianzhu (Heavenly Candle) peak. There's still a little way to walk upwards from where the bus drops you off to the ticket entrance. Ticket price to go all the way to the end is 3 RMB/person, journey time took about 45 mins (we started around 0700 IIRC).