Udaipur is called as Venice of the east filled with lot of lakes and palaces. With history from Mewar kingdom, Udaipur is popular for islands too. July is called as Rainy month of udaipur, where rains are less and humidity is more. Valley of flowers is one of the most described paradise spot of Himalayas which is a. unesco world heritage site. Filled with lovely flowers blooming new in July, trekking is popular here. It is rainy month and few downpours are expected though not heavy. My suggestion would be Valley of flowers, for you can plan udaipur after September when weather is really cool.
Valley of flowers trip is an apt monsoon trip, but weather is the uncertain factor which decide whether one can have complete fulfilling experience or partial. I went there along with Hemkund last year in full forecast of heavy rains but got lucky to face little rain only so the entire experience was unique and fulfilling. In case you plan then do plan taking weather forecasts in consideration.