Show all before select

Hello to all,
I have a table that show all providers by town where they to provide services. I have a select field where the user will select the town to show in the table. I would like to when the user enter in the site for the first time show all the providers and then, the user will select the town from the select field and will show only that town. The second part is fine, at this moment the user get in and select the town and it works but always when they get in the site is showing one town only. I would like to show all.
Thanks