How to create a taxonomy terms dropdrown with Views
There are several approaches:

A. Create a View out of Taxonomy Terms with a Page Display. 

For fields add: term id, term name
For filters: Term name (with widgets) and expose the filter

Choose then: 


Dropdown,
Vocabulary (of your choice)
Expose this filter to visitors...,
'Is one of' then select all terms from the vocabulary
Remove duplicates


In Views UI, on Advanced Tab


Exposed form in block: Yes
Exposed form style: Basic | Settings
Adjust settings to have autosubmit


B. Create a View out of Content and choose Taxonomy Terms among fields, similar to above.

C. Create a View with Block display from Taxonomy Terms and at Format Tab choose Jump Menu. If you need to overwrite the Jump Menu path you need to add a custom text field and create your desire path out of Replacement Patterns.

Than select the created custom text field from Jump Menu path settings