This answer assumed the user is already in 'Edit' mode
You've mentioned that this list view is used by the user to add and delete accounts.
In this scenario deleting should be a primary action which means you can forego hiding the delete action behind the long press.
If the user needs to receive feedback for account deletion, then make the delete button available for each account. You can then provide feedback as each account is removed.
In cases where the items do not require individual feedback, you can make available check boxes and allow for a bulk delete action. Using the action bar for this scenario makes sense.
See http://developer.android.com/design/patterns/actionbar.html for more info
Edited answer based on additional info
A typical function of a list item is allowing the user to drill down into the detail view of a selected list item.
I rarely come across a reason to allow the user to perform destructive actions alongside non-destructive ones. Users should feel comfortable navigating a list of item without the fear of doing something wrong. Therefore I'd hesitate to add the stress of avoiding delete buttons if the user is drilling down on account items.
Its with this mindset that we only activate the destructive interactions at the users' instigation such as:
- Swipe to delete (iOS pattern)
- Long press to present contextual actions (android pattern)
- Tap a checkbox on a smaller target within the list item
- Tap 'Edit' to enter editing mode
You can adopt any of these designs options by weighing up user's intent when they enter your page. Are they intent on 'editing' their accounts list or are they browsing their list.