Manta is a generally safe city but tourists should take special care in certain areas. Dark unlit streets at night is an invitation for trouble. Taxis are inexpensive in the city, using them even for short distances is a great precaution.
Travelers in Manta and other areas are likely to be approached at some point or another by con artists or persons with "sob stories". Ignore such persons and be wary of anyone asking for money under any pretext, including children begging. If you're feeling charitable, Ecuador has lots of legitimate charities you can support. Pickpocketing is done by highly skilled groups of 3 or 4 people. You are best off not bringing a wallet at all -- just some bills split between various pockets. Buses and bus stations is an area known to target travelers foreigners or locals alike. You need to watch your bags closely, before and during departure; even once on the bus. It is best not to put your luggage in the overhead shelving, as you can be easily distracted and have all your possessions stolen before realizing it.
Do not leave drinks unattended in bars and restaurants especially at night. Thieves working in tandem are known to act friendly gaining your confidence; then 'slip you a mickey' spike your drink with drugs, and then rob you.
local laws and the ecuadorian national police
All Ecuadorian citizens and visitors are required to carry ID at all times. Carrying your passport around all the time is not advised due to the risk of loss of theft. A better option is to have a copy of your passport certified by your embassy and carry that with you.
blend in and avoid con artists
Wearing gringo' clothesi.e. fishing vests, travelers pants, bright colored t-shirts, dirty sandals will make you a target. A pair of nice pants and a nondescript white/off-white t-shirt will make you look a business person who knows his way around the area and not just another tourist