This...

'28 DB0 - PORTA.0
'29 DB1 - PORTA.1
'30 DB2 - PORTA.2
'31 DB3 - PORTA.3

is not compatible with this...

DEFINE LCD_DREG PORTA 'LCD data port
DEFINE LCD_DBIT 4 'LCD data starting bit 0 or 4

...and double-check with the Datasheet that you've disabled all Analogue Functions on PortA.