Hi,
No, PICaxe Basic doesn't support a port.pin name for Leg2, and there is only "partial" support for A.0 / Leg19 (IIRC it can't be symbolised).
But you should be able to Read/Write the SIn pin via a PEEK/POKESFR command, which is "Bit 5" in "Port A". The address seems to be $0C for the port, and banks 1 ($2C) and 2 ($4C) for the TRIS and LAT flags respectively. Also the Weak Pullup Resistor is available via bit5 of the WPUA SFR.
Beware that other pins of the base PIC's PortA are mapped onto the PICAXE's Ports B and C.
Cheers, Alan.