Please try this code:
$websiteId = Mage::app()->getWebsite()->getId();
$groupId = Mage::getSingleton('customer/session')->getCustomerGroupId();
$ruleName = /* your rule name */;
$rules = Mage::getResourceModel('salesrule/rule_collection')
->setValidationFilter($websiteId, $groupId);
$rules->addFieldToFilter('name', $ruleName);
$rules->getSelect()->limit(1);
$rule = $rules->getFirstItem();
echo $rule->getSimpleAction(); // by percent ...
echo $rule->getDiscountAmount(); // amount
Edit: to get all rules you can try this (not tested yet)
$websiteId = Mage::app()->getWebsite()->getId();
$groupId = Mage::getSingleton('customer/session')->getCustomerGroupId();
$rules = Mage::getResourceModel('salesrule/rule_collection')
->setValidationFilter($websiteId, $groupId);
foreach ($rules->getItems() as $rule) {
echo $rule->getSimpleAction(); // by percent ...
echo $rule->getDiscountAmount(); // amount
}
Mage::getSingleton('customer/session')->getCustomerGroupId()