Basic rule and daily life about Dhaka city and Bangladesh, specially for the tourist. Bangladesh is a very safe and nice countries and Bangladeshi people is very friendly. Any tourist allowed to meet with public and avoid gathered places for avoid un-wanted risk. Some road of Dhaka city is very clean and wide, perfect for walking on Road.
Malaria Problem: Except some hill cities as like Khagrachari, Rangamati and Bandarbans districts, whole Bangladesh is Malaria free. So, if you don't go inside hill tracks, no need to take vaccines.
Security : Basically Bangladesh is a safe area than some neighboring countries as like India, Myanmar, Nepal etc, specially for the foreign tourist. Because here foreign tourist treated as Gov. Guest and police is also very serious about them. So, usually pick pockets also avoid foreigners tourist. Just follow the general security rule and avoid dark places, lonely streets, tour operator, fake offer from travel company, you will be fine here.
Hotels : I found Tropical daisy expensive. Better you stay Hotel Rajmoni Ishakha ( 89/3 VIP Road, Kakrail, Dhaka. Mail: email@example.com , Royal Palace. In these hotels you will get good rooms within $25-$30 USD.