Magento – Edit layered navigation filter titles in Magento 1.9.2

if you need to define custom price ranges for each category.follow the following steps

1) Go to System > Configuration > Catalog > Layered navigation.In this select Manual from "Price Navigation Step Calculation" and add following configuration from the following image.

2) Now go to any category and go to "Display Settings" tab their see at the bottom you can see "Layered Navigation Price Step" just give the Price Step for that cateogry. for more details see the image.

Price Step is basically the difference between the upper limit and lower limit in that price range.

You can use magento registry variable

Mage::registry('current_category')

or use

Mage::getSingleton('catalog/layer')->getCurrentCategory() for getting current category object

Second option is best