Mumbai/Thane to Mount Abu/Udaipur is a popular driving holiday route, featuring excellent roads, many of them six-lane. Unless the monsoon creates exceptional havoc this year, there is no reason to fear a driving trip on this route in September. The rider being, of course, that all driving, anywhere, in the monsoon should be attempted with greater caution than in dry weather. Since the drive time is estimated as being 12-13 hours, your plan to break journey in Vadodara makes perfect sense.
As far as attractions in Mount Abu go, the stunning Dilwara Jain temples take pride of place. Built between the 11th and 13th centuries, these lovingly preserved temples display fine craftsmanship in marble and are a draw for pilgrim and tourist alike. The Achalgarh Fort outside town makes for a good half-day excursion and offers lovely views of the surrounding hills. Apart from this, Rajasthan’s only hill station has various ‘viewpoints’ that afford soothing vistas of green. The town also has a lake that may be worth a visit, especially if the monsoon does its thing well.
In Udaipur, the lake is, of course, the centre of attraction. Lake Pichola is a storied thing, with much of the town’s considerable built heritage constructed around—and on—it. Take a boat ride on the lake, spend an hour or two at the lovely City Palace complex, drive up to the Monsoon Palace, visit the Eklingji temple and visit Bagore ki Haveli.
Haveli stays are easily had in Udaipur. One of the most refined is Amet Haveli (from ? 6,800 doubles; www.amethaveliudapur.com). But my vote goes to the well-run Jagat Niwas Palace (never fear, it’s a restored haveli, not a palace). Lake-facing rooms here cost from ? 4,250, but standard non-lake-facing ones are available from ? 1,850 (www.jagatniwaspalace.com). Other options include Udai Kothi (from ? 5,500; www.udaikothi.com) and Karohi Haveli (from ? 2,800; www.karohihaveli.com). Mount Abu, unfortunately, does not offer any heritage accommodation. The closest it gets is Hotel Silver Oak, set, it is claimed, in a colonial building (from ? 4,000; www.hotelsilveroak.com). Other popular choices are Hotel Hillock (from ? 6,000; www.hotelhillock.com) and Ratan Villas (from ? 6,000; www.ratanvillasmountabu.com).