You should just create your list like:
<select name="contract_signed" id="contract_signed">
<option value="1">yes</option>
<option value="2">no</option>
</select>
Then highlight the list and click the dynamic button in the properties panel. Then chose the set selected value equal to: $row_WADAprop_address['contract_signed']
and DW will write the code for the list to select the correct value and you can still update it.